MEXICO CITY, Sept 12 (Reuters) - Along with the thousands of stockbrokers, investment bankers and office workers, a small army of poorly paid Hispanic immigrants were in New York's World Trade Center when its mighty twin towers collapsed after a terror attack on Tuesday.

Most went to New York in search of a better life and, although they only made $200 a week, their jobs meant they could send a little money home to help their families.

It seems certain scores, maybe hundreds, are now among the victims buried in the smoldering rubble of concrete and steel.

Most of the immigrants were Hispanics, mainly from Mexico, Central America, Puerto Rico and the Dominican Republic, but there were others from across the world.

They had jobs in the World Trade Center's restaurants and in its shops. Others cleaned its floors and still more worked in fast-food joints in southern Manhattan and would have been making breakfast deliveries to office workers when two hijacked planes slammed into the 110-story landmarks.

Some had been in New York for years and had their families with them. Others were alone and - if they were working with false papers and are among the dead - finding their families could be a mammoth task.

"There are lots of youngsters here without their families. So we are calling on their friends and room-mates to call and tell us if they didn't come home last night," said Esperanza Chacon, the director of urgent affairs of Asociacion Tepeyac, a group giving legal and social support to Mexican immigrants.

Along with Mexico's consulate in New York, Asociacion Tepeyac is working the immigrant community network to find out who worked in the World Trade Center and determine whether they are safe or are still missing.

"I know some are buried in that rubble. It was impossible to get out of there," said Arnulfo Rojas, a 33-year-old Mexican who worked in the kitchen of the Hudson River Club restaurant in one of the smaller towers of the complex and escaped the disaster.

On Tuesday, knife-wielding hijackers crashed commercial jets into the World Trade Center in New York and the Pentagon near Washington in the worst attack on the U.S. mainland in modern history. A fourth hijacked plane crashed in Pennsylvania.

Thousands of people were feared dead after the assault on the symbols. Senior U.S. officials, who were exploring many different leads, said the coordinated strikes could be linked to the organization of Saudi-born Osama bin Laden.

Mexico's consulate said on Wednesday it received 400 calls from people trying to contact their relatives in New York.

Aside from the well-established Hispanics employed as bankers, brokers, analysts and office workers in the World Trade Center, hundreds more were in low-paying jobs.

Rojas, a migrant from the central Mexican state of Puebla who has been in New York since 1988, said some of those were illegal immigrants working with bogus papers and that they made a little over $200 a week with tips.

Chacon said her group had already identified a dozen missing Mexican migrants and was trying to contact family members in the United states and at home in Mexico. They were also looking for many others after calls from anxious relatives but had so far come up with very little.