At least 50 people are confirmed dead and more than 700 others injured in Argentina after a busy commuter train crashed into a barrier at a Buenos Aires station.

The train came in too fast and hit the barrier at the end of a platform at Once station during Wednesday morning's rush hour, smashing the front of the engine and destroying the coaches behind it.

"Never in my life had I seen anything like this," Juan Schiavi, Argentina's transportation secretary, said. "Cars piled up on top of each other and one of them went six metres inside another car."

In a statement, Cristina Fernandez de Kirchner expressed "deep regret" over what she said was a "tragic accident", sent condolences to the families of the victims and ordered two days of national mourning.

The government also suspended carnival celebrations, including a massive parade planned in Buenos Aires on Friday.

Monica Yanakiev, a journalist at the scene of the train crash, told Al Jazeera, that the accident left many people trapped for hours amid the wreckage, with ambulances filling the streets.

"There are three or four hospitals that are crowded with victims," said Yanakiev.

Heavily damaged

The most damage occurred in the first coach, where passengers make space for bicycles. Survivors told the TeleNoticias television channel that many people were injured by metal and glass.

Passengers said 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 crash.

Rescue workers searched for survivors after Wednesday's accident at the Once railway station

"People started to break windows and get out however they could," one survivor said.

"Then I saw the engine destroyed and the train driver trapped among the steel. There were a lot of people hurt, a lot of kids, elderly."

Many people with lesser injuries were waiting for attention on the station's platforms as helicopters and more than a dozen ambulances took the most seriously injured to nearby hospitals.

The driver was among those taken to hospital for treatment, said Ruben Sobrero, union chief on the Sarmiento line, the commuter rail service in the Argentine capital.

Sobrero told local media that reports speculating the crash was caused by the train's inability to stop fast enough due to brake problems could not be verified.

"This machine left the shop yesterday and the brakes worked well," he said. "From what we know, it braked without problems at previous stations. At this point I don't want to speculate about the causes."

The Sarmiento rail line, owned by private company TBA, links the centre of Buenos Aires to a densely populated suburb 70 kilometres to the west of the city. It uses rolling stock made in Japan and acquired in the 1960s.

TBA said it did not know the cause of the crash and would bring "all information and videos to the courts."

Argentina has seen five serious train accidents since December 2010. The deadliest of these prior to Wednesday happened last September, when a bus crossed the tracks in front of an oncoming train, killing 11 people.

Source: Al Jazeera and agencies