Many commuters are furious that the government appeared to ignore repeated warnings about train issues [AFP]

Faulty brakes caused the train accident in Buenos Aires that killed 51 people on Wednesday, an engineer operating the locomotive has said, according to an Argentine judicial source.

Marco Cordoba, who is being investigated by police but is free after being treated, said on Saturday he had repeatedly warned the brakes were defective.

He told police he reported brake problems to his supervisors but that he was ordered to continue the trip that ended in the third worst rail accident in Argentine history.

Cordoba was free after authorities determined he represented "no flight risk and there is no possibility he might hinder the investigation", the judicial source said.

At least 703 people were injured when the commuter train, carrying about 2,000 people, crashed into a bumper at Buenos Aires' Terminal 11.

Argentines who lost relatives in the crash and many commuters were furious that the government appeared to ignore repeated warnings about problems with the country's trains.

Relatives of the 51st victim, whose body was recovered on Saturday though initially it did not appear on any lists of the dead or injured, kept vigil at the train station and threw objects at passing buses and taxis.

An Argentine association that represents government employees accused the government on Friday of letting passenger rail infrastructure fall into disrepair.

'Deficient preservation'

A statement from the group said the government ignored an audit "that showed the deficient and criminal state of preservation" of the Sarmiento rail line, where the accident occurred.

Corodoba, 28, was among the injured who had to be cut out of the locomotive cab by firefighters. He was hospitalised for cuts on his face and other injuries, but was out of danger.

The judicial source said Cordoba told investigators: "At each station he advised the dispatcher by radio that he had problems with the brakes."

He reportedly said he was told to keep going.

Immediately after the accident, the national transport secretary, Juan Pablo Schiavi, said recordings between the engineer and dispatcher would be reviewed by the authorities.

Blood tests showed he had not been drinking or using drugs. He also had a good work record.

The severity of the rail disaster for Argentina ranked behind only the 1970 train accident in Benavides that killed 236 people and the 1978 wreck in Santa Fe province that resulted in 55 deaths.