A commuter train crash west of Buenos Aires has killed at least three people and injured more than 200, authorities have said.
A two-level train slammed into another that had stopped between stations near the Castelar stop in Moron, 30km west of the capital during the morning commute on Thursday.
Dozens of firefighters, paramedics and police pulled passengers from the wreckage, and helicopters and ambulances took people to hospitals.
The company operating the Sarmiento line said it was not yet clear what caused the crash, which occurred at 7.07 am (10:07 GMT), but that the train had sped past a "caution" signal to slow down and three "danger" signals ordering it to stop.
"I heard a loud noise and everyone started falling down, and people were shocked and crying," said a 26-year-old passenger who identified herself as Lida.
Interior and Transport Minister Florencio Randazzo said service would be interrupted for 24 hours "so that an in-depth investigation may take place."
"We wish to know beyond a doubt if it was criminality or an accident," the minister said, adding the train had been equipped with new brakes.
However, union leader Ruben Sobrero said at the scene that the two-level train had been out of service for six months before it was brought back online shortly before the acccident. Gunning said the engine had new brakes installed.
The driver of the train, who was injured in the crash and taken to a hospital, has not yet commented on the incident.
The accident happened on the same Sarmiento line that the government took over after another wreck blamed on brake failures caused 51 deaths and 700 injuries last year.
After last year's wreck at the Once station, President Cristina Fernandez promised to prosecute those responsible and make new investments in safety.
She revoked the concession run by Mario and Sergio Cirigliano, two brothers who own many companies involved in
maintaining Argentina's rail systems, and formed a state-supervised consortium of companies to operate the commuter lines.
The Cirigliano brothers are among more than two dozen defendants awaiting trial on criminal charges stemming from last year's crash, but they remain deeply involved in Argentina's train system.
Survivors of that crash complained that it was the Cirigliano brothers' shop that worked on the brakes of the train that failed to stop in time on Thursday.
"The train that hit the other was repaired in EMFER, which is controlled by the Ciriglianos, the businessmen responsible for the tragedy,'' said Paolo Menghini, who lost his son Lucas in the Once station crash, according to the local DyN news agency.
"They cannot be sending trains to be repaired at EMFER.''