A packed train slammed into the end of the line in Buenos Aires’ busy Once Station on Wednesday.
Local authorities said 49 had been killed and at least 550 had been injured in the accident. Emergency personnel were still working to resuce some passengers trapped inside the wreck.
"Unfortunately, we must report that there are 49 dead in the accident," including a child, police spokesman Nestor Rodriguez told a news conference.
The train's driver was injured, but rescue workers pried him loose from the wreckage. Local television showed him and several others being carried away on stretchers.
According to Argentine Transport Minister JP Shiavi, the c mmuter train came in too fast and hit the barrier at the end of the platform at about 12 mph (20 kph).
The impact smashed the engine and leading cars behind it. One car penetrated nearly twenty feet into the one in front of it, while following cars "split apart."
Survivors told the TeleNoticias channel that many people were injured in a jumble of metal and glass. Passengers told the channel windows exploded as the tops of train cars separated from their floors.
The trains are usually packed with people standing between the seats, and many were thrown into each other and to the floor by the force of the hard stop.
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.
Wednesday's train wreck is the most deadly train accident since Feb. 1, 1970, when one train smashed into another at full speed in suburban Buenos Aires, killing 200 people.