CULIACAN ? (UPDATE) Three trains, one apparently carrying undocumented migrants, crashed in a fiery pileup Tuesday in northwestern Mexico, killing at least 11 people and leaving four more hurt, authorities said.

The accident took place early Tuesday on the track at a station in the town of El Fuerte in Sinaloa state.

"There are 11 people killed, including a mechanic, as well as four people injured," Sinaloa civil defense chief Miguel Diaz told Agence France-Presse.

A train coming from the western city of Guadalajara apparently suffered a brake failure and crashed into two other trains, one of which was carrying out a maneuver on the track, according to Diaz.

Some 300 rescue workers toiled at the massive accident which involved a total of 75 train cars.

At least three more people were trapped in the rubble, and it was not known if they were still alive, Diaz added.

Earlier the state prosecutors' office had reported the accident involved two trains.

Authorities believe the people killed were stowaways trying to sneak illegally into the United States, because there were no passenger trains involved.

Mexican freight trains are used by an estimated 500,000 people every year to try to enter the United States illegally.

The United States has an estimated 12 million illegal immigrants, most of who enter from neighboring Mexico.