There were there were "various deaths," said Pablo Gunning, a spokesman for the government-run agency that took over the commuter line after an earlier crash killed 51 people last year. Government ministers at the scene were preparing for a news conference and would not confirm how many.
It wasn't immediately clear why the leading train had stopped between stations, and why the train behind failed to stop in time.
Union leader Ruben Sobrero said the two-level train had been out of service for six months before it was brought back online shortly before the accident. Gunning said the engine had new brakes installed and had been approved for service.
The accident happened on the Sarmiento line carrying passengers from the downtown Once station to the suburbs, and so the cars were much less full of passengers than those carrying commuters to work in the city.
After last year's wreck at the Once station, which also injured 700 people, 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 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."