The collision occurred after the train's brakes failed, as it was arriving at a station on the western outskirts of Buenos Aires.
The total number of casualties surpassed the city's last major rail disaster just five months ago when two trains and bus collided during rush hour, killing 11 people and injuring more than 200.
COMMENT: The Sarmiento rail line, which links the center of Buenos Aires to a densely populated suburb 70 kilometers (44 miles) to the west of the city, uses railway cars acquired in the 1960s.
In March 2008, 18 people were killed and 47 injured when a bus was hit by a train in Dolores, 212 kilometers (132 miles) south of Buenos Aires. Argentina's deadliest train tragedy was in 1970, an accident that killed 200 people north of the capital.
Unfortunately, Argentina's overcrowded and poorly maintained rail system, run by private companies and heavily subsidized by the government, are plagued by accidents and delays.
One the most significant lessons learned from today's collision is that Argentina, like many countries around the world, are not well prepared for a mass-casualty event, regardless of the cause.