At least 49 people were killed and more than 550 others injured here when a commuter train crashed and derailed during Wednesday's morning rush hour at Once Station in the city center.

It is one of the worst railway tragedies in the country since February 1970, when a train from Tucuman province in northern Argentina crashed into another, which had come to a halt due to mechanical failure, claiming 236 lives.

The following is a chronology of Argentina's rail accidents in the last two years.

2011:

Nov. 2 -- Six girls and two teachers from a private Catholic school were killed and another 41 others injured when a freight train crashed into a bus at a crossroad in the central province of San Luis.

Sept. 13 -- A total of 11 people were killed and more than 200 others injured in a train crash on the central Sarmiento line in western Buenos Aires.

April 4 -- At least 70 people were injured following a collision between a locomotive and a train in Lezama, some 157 km south of Buenos Aires.

Feb. 16 -- Four people were killed and more than 100 others injured when a Ferrobaires train bound for Junin in Buenos Aires province crashed into another from the San Martin company near the San Miguel station.

2010:

Dec. 31 -- About 50 people were injured when two trains from Mitre Railway collided at the Maldonado station in Buenos Aires.