ELECTRONIC sentry tower stands guard over US / Mexican border. Last fall, a large influx of immigrants from Central and South America arrived at Windsor after crossing from Detroit. Most of the 200 or so were Mexicans who had been living and working in the United States illegally.

Their exodus began after an immigration bill that would have provided a path to citizenship for undocumented migrants was defeated in Washington. Talk of legislation that would levy fines on companies and individuals who employed such migrants only spurred them to head north.

If reports were accurate, they were counselled - for a fee in most cases - that rather than returning to their countries of origin they could apply for refugee status in Canada. Mexicans do not require a visa to enter Canada.

Most of the applicants have family members with them and their presence causes major problems for local social service agencies. They must be fed and housed until they either are returned from whence they came, or, if their applications are accepted, they find gainful employment and began supporting themselves.

To date, the relatively low number showing up at Canadian border cities has not led either to calls for stricter rules or a public outcry against the newcomers.

The situation is much different in the U.S. southwest, where Mexico and four American states share a 3,169 km-long border. At its eastern end, a 2,000 km stretch of the Rio Grande River separates Texas from Mexico. In some areas the river can be easily forded at certain times of the year. Much of the border west from El Paso, Texas, consists of remote, rugged, and sparsely populated areas of New Mexico, Arizona and California.

The number of undocumented aliens (UDAs) attempting to enter the US each year is astounding. They are referred to as UDAs because they do not have proper documentation to enter the US, even though most have identification papers, either real or bogus, from their home countries.

In 2005, for example, various agencies intercepted and detained 1.2 million border crossers, 90 per cent from Mexico. Other Central and South American countries account for the balance, although citizens of 150 different countries have been arrested while crossing from Mexico since the 9/11 attacks on America.

Most of the detainees are returned to Mexico within 24 hours. Many try again the same night or the next day. Depending on whose figures you believe, only one in four or five border crossers are caught. There are believed to be up to 12 million UDAs in the U.S. at present.

Many did enter legally, having been granted a three-month visa for seasonal work in the vast agriculture industry in Arizona and Southern California. An average of 50,000 such visas have been issued in each of the past three years. Approximately 20% of applications are rejected one reason or another and the process is time-consuming and costly for the individual. Efforts by American farmers who employ the labourers have not been very successful in attempting to simplify and speed up the paper work. Much of the fruit and vegetable crops for sale in our local supermarkets have been grown on farms where most of the workers came from Mexico, lured by wages four to five times higher than they could make at home.

But a high percentage of those granted temporary visas don't return home. Up until the subprime mortgage crisis blossomed last year, they had no trouble finding jobs in the booming construction industry in the Southwest. Others moved on to northern cities, taking jobs in the service industry shunned by American workers because of the low wages offered.

For years this influx was not seen as a major problem by the federal government, and only occasionally drew the attention of the national news media. However it is a different story in Arizona. Very few days go by without a story in the local news about border crossers, particularly in Tucson, a city of one million, just 50 miles north of the border. Phoenix, the state's capital and largest city, a further 100 miles north, is similarly affected.

If aliens make it across the border undetected, they are usually picked up and driven to a safe house in or near either city. Here they wait for the next leg of their journey or melt into the city, with the help of friends or relatives already in the US. They may have paid from $1,000 to $2,500 to the human smugglers - known as 'coyotes' - to get them this far. If they are caught making their way through the desert, at a Border Patrol checkpoint, or when a safe house is raided, there are no refunds. They are at the mercy of these 'coyotes' from the time they take their first step into US territory.

Tragically 1,137 aliens, mostly women and children, have died in the desert or mountains of the Tucson sector since 2000, abandoned by their uncaring guides because they couldn't keep up with the group. And getting lost or running out of drinking water, when the daytime temperatures reach 110F [44C] in July and August, is usually fatal. During the same period two to three times that number were rescued by Border Patrol agents.

Funding for the Border Patrol is a federal responsibility. The number of agents has risen from 6,000 to 15,000 in recent years and recruiting for a further 3,000 is ongoing. Most of the costs associated with the UDAs, once they have made it into the US, however, are borne by local jurisdictions. Accidents involving overloaded pickup trucks or vans are an all-too-common occurrence. The mishaps usually happen at night on highways or back roads between the border and Tucson.

A typical accident occurred on April 7th, at about 5 a.m., 20 miles east of the city. A van with 32 people jammed inside veered off the road and rolled down an embankment, leaving one woman dead, five or six critically injured, and the rest with minor injuries. Helicopters were needed to ferry the injured to four Tucson hospitals.

The most seriously hurt will probably need care for weeks until they are well enough to be deported. It is difficult to put an actual dollar figure on the cost to Tucson medical facilities, but estimates range as high as $3 million annually. Federal funds only pay a small percentage of the total.

One recent study put Arizona's annual cost from illegal immigration at $1.3 billion - $810 million for education; $400 million for health care related expenses; $80 million in incarceration costs; and the rest on welfare benefits. The state's annual deficit has been as high as $500 million in the past few fiscal years.

UDAs, as a rule, are not a big problem for law enforcement authorities once they have made it into the country, found a job and housing for their families. The same can't be said for the small percentage involved in drug trafficking. Marijuana, methamphetamine and other illegal substances are seized in ever-increasing quantities every year.

Annual seizures in excess of 500,000 pounds of marijuana are common, hidden in vehicles of all descriptions, carried on mules, or on the backs of individuals. How much makes it through undetected is anyone's guess.

According to Tucson police, 50 per cent of crimes they investigate now are related to methamphetamine trafficking. And violence against police and Border Patrol agents is on the rise.

Last November, a Border Patrol agent was run down and killed southwest of Tucson by drug smugglers driving a Hummer vehicle. On April 4, local TV news carried two more stories highlighting the seriousness of the problem. In one report, a so-called safe house was discovered on the city's south side with 20 illegals inside, crammed into its 1,000 square feet.

In the second, a young man was arrested with a cache of handguns and automatic weapons. He is a resident of a New Mexico border town and police believe the weapons were bound for drug cartels across the border.

This is the first of a twopart series. A former Citizen columnist, Graham McLeod and wife Pat were in Arizona earlier this year. In the concluding article, Graham tells of one rancher's approach to the border crossing problem.