Many Latin Americans make the hazardous journey to the US each year

Mexico says the deaths of 18 suspected illegal immigrants who suffocated inside a trailer in Texas shows the need to legalise the migration of workers across the US border.

A Mexican foreign ministry statement condemned what it called "this lamentable incident" and promised co-operation with the US in tackling immigrant trafficking.

The grim discovery of the bodies at a rest stop in Texas was one of the worst cases of people smuggling in the border area in recent years.

Survivors have been speaking of their desperation as they struggled to escape from the back of the tractor-trailer where it is believed up to 100 people were crammed.

One person inside the sweltering container used a mobile phone to make an emergency call, pleading in Spanish for help as people suffocated.

But the call could not be traced.

Police eventually found the trailer at a truck rest stop near the city of Victoria, about 370 kilometres (230 miles) from the Mexican border early on Wednesday.

The victims - many of them Mexicans but some from Central America - appeared to have died from suffocation and heat exhaustion, US officials said.

Desperation

Some of the 39 survivors in US custody have told Mexican consular officials that smugglers loaded them onto the trailer on Tuesday and the air conditioning inside at first worked well.

But when the driver unhooked his cab and abandoned the trailer some hours later, it soon became airless.

"In desperation, the people said they broke out the truck's taillights to try and attract someone's attention and perhaps get some air," Marco Nunez of the Mexican consul's office in Houston told AP.

Some of the victims were said to have torn off their clothes because of the heat.

Police have arrested the trailer's registered owner and are were still looking for two other people, US officials said.

The authorities also believe 40 illegal immigrants who tumbled out of the vehicle alive when it was opened managed to escape.

The Mexican Government has long pressed Washington to make it easier for Mexicans to come to the US legally.

Every year thousands of Latin Americans make the hazardous journey and are often at the mercy of smuggling gangs.

"This lamentable incident shows the need for and importance of achieving safe conditions on the border for migrants and the need for safe, legal and orderly migration," the foreign ministry statement read.

"The Mexican Government reiterates its commitment to fight gangs of immigrant traffickers and those who seek to profit at the expense of undocumented migrants."