Soldiers were called out Friday to help dig for people missing in the rubble of a collapsed building that killed at least 13 the day before.

Red Cross and state government officials confirmed the number known dead and said 53 people were injured.Gilberto Sanchez, radio officer at police headquarters, said about 60 soldiers from the army garrison joined firefighters, police and volunteers in the rescue effort. Bulldozers and cranes were brought from as far away as Salamanca, 78 miles to the southwest.

Aguascalientes, a city of about 500,000 people 320 miles northwest of Mexico City, is the capital of Aguascalientes state.

"Hundreds of people have come to help in the rescue of an undetermined number of people who are missing . . . although as time passes our hopes of finding survivors diminish," said Juan Diaz, head of special services for the local Red Cross.

He said at least 116 workers were in the building when the four upper stories collapsed. Diaz was reached by telephone from Mexico City.

"Relatives of the victims practically attacked the ambulances, trying to identify" the victims, he said.

The building, still under construction, consisted of three basements, a main floor and three upper stories.

As workers were about to pour the last concrete late Thursday afternoon, it collapsed onto a furniture factory that occupied the ground floor and part of the basement area.

Lower floors of buildings in Mexico often are occupied while the upper stories are constructed.

Roberto Padilla, an Aguascalientes state government spokesman, said the state attorney general's office was investigating the collapse of the building, which was three blocks from the main plaza and the state capitol.

Jorge Castaneda, head of the Aguascalientes Civil Engineers Association, said a committee of engineers and architects also would investigate.

Juan Navarro, a police duty officer, said by telephone: "They were apparently pouring fresh concrete when it caved in. Apparently the building did not resist the weight."

Juan Flores, a survivor who was buried for five hours, was quoted by the Excelsior news agency as saying:

"I had finished working and was about to leave when . . . all of a sudden everyone started yelling hysterically that there was an earthquake. I dashed under a table and all of a sudden everything went dark, and there was this terrific noise and there was dust everywhere."