Argentina's President Cristina Fernandez de Kirchner expressed her “profound sadness” over Wednesday's train crash in Buenos Aires, which left 49 people dead and more than 600 injured.

The accident was the worst rail disaster in the country in 30 years. On Wednesday morning, a packed commuter train slammed into the end of a platform at the Once station in the center of the capital. According to reports, the train had a total of 1,200 to 1,500 passengers on board and was traveling at 16 miles per hour.

The train was full and the impact was tremendous, a passenger named Ezequiel told local television news program.

As rescuers continue to pry apart the ruined train cars in hopes of finding survivors on Thursday, authorities are trying to find out what caused the accident. Transportation Secretary Juan Pablo Schiavi believes that the crash was caused by a break failure.

The train was owned by private company Trenes de Buenos Aires SA, the same company that owned the train that crashed in Buenos Aires last September, killing seven people.

“I said, ‘Be careful, the train isn’t braking’… I moved backwards because I thought it was going to run me over,” Alfredo Velazquez, who was waiting on the platform, told Reuters.

“There was a terrible explosion and a brutal impact,” he added. There were people who were crushed and shouting desperately. I saw bodies and blood all over the place.

According to passengers, after the impact people “flew through the air” and where tossed around the crowded cabins. Some commuters jumped out of windows as train cars buckled and drove into the vehicles in front of them.

Trenes de Buenos Aires has begun investigating the incident, and said it would bring surveillance video footage to the proper authorities. The train's driver, who had an excellent record, according to the Agence France Presse, survived the crash.

It is still quite safe, Juan Alberto Roccatagliata, the director of the National Rail Authority until 2010, told BBC of Argentinian train travel.

However, investment levels and maintenance have not been up to what is required to reduce the probability of things like this happening.

President Kirchner declared two days of mourning and cancelled the Carnival parades and celebrations for the rest of the week.

Meanwhile, the relatives of passengers continue to search the city's hospitals and morgues for their loved ones. Hospital officials are reportedly not giving out the names of the patients with the worst injuries until after surgery.

The worst train accident in Argentina's history happened in February 1970, when two trains collided at full speed in a Buenos Aires suburb, killing 200 people.