Authorities in Mexico's east-central state of Veracruz discovered 31 undocumented immigrants from Central America locked in a truck trailer Sunday and have detained the Mexican driver and two other companions. This was only the latest incident in which immigrants have been found in life-threatening situations.

Police spokesmen say agents made the discovery after stopping the truck to check its documents and cargo. The policemen heard noises from inside the trailer and from small holes that had been broken into the side of the trailer. After opening the door, the police found the immigrants, including seven women and two children.

They later determined that the immigrants came from Gualtemala, El Salvador and Honduras and had paid for passage northward through Mexico. One of the detained immigrants spoke to Mexico's Televisa network from his jail cell.

He said he and the other illegal immigrant passengers had suffered hunger and thirst for some days in the cramped, windowless trailer and that they thought they might die.

Last week, authorities in southern Mexico found 92 Central American immigrants packed into a similar truck heading north. The police surveillance of trucks follows the death of 19 immigrants trapped in an abandoned trailer on a Texas highway on May 14. After completing their investigation and arresting several suspects in the case, U.S. authorities sent the bodies of the 12 Mexican victims back to their families for burial. The funerals of these and other immigrant victims have been given ample coverage in the Mexican media. Last year 371 Mexicans died in the attempt to cross illegally into the United States seeking work.

But the plight of Central Americans has not received as much attention in this country. Human rights groups say tens of thousands of Central and South American immigrants pass over Mexico's southern border with Guatemala each year. Mexican authorities detained and deported more than 57,000 immigrants on the Guatemalan border last year.

For the most part the immigrants crossing over from Central America are headed for the U.S. border, nearly 3,000 kilometers to the north. Human rights groups working with immigrants in that region say they have received thousands of complaints against Mexican police for abuse of undocumented immigrants. Mexican authorities say they are working with neighboring nations to prevent immigrant deaths and injuries.