The driver of the derailed Spanish train, which killed at least 80 people, had reportedly bragged about running at high speed in the past, suggest reports.

Francisco José Garzón Amo is under investigation by the Spanish authorities, who believe the train was running at twice the actual speed limit while negotiating a curve.

Four of the train's carriages derailed and slammed into barricades while running near the northwestern city of Santiago de Compostela in one of the deadliest train disasters in recent history.

According to local reports, the driver of the crashed train posted pictures of him operating trains at high speeds in March 2012.

Screengrabs showed Garzón posting a picture of a speedometer clocking 200 km per hour. However, the Facebook account has been deactivated in the wake of the derailment. It is not sure whether the account belongs to the driver.

One of his friends commented on a picture: "Woah you are going so fast, braaaaaaake."

Garzón replied: "If I went any faster, they'd fine me," adding: "The speedometer doesn't lie."

Pending questioning by the Spanish police, an initial investigation has ruled out he was under the influence of alcohol.

Garzón, who suffered minor injuries in the accident, "would be questioned by police in hospital where he has been placed under surveillance," the high court in Galicia said in a statement.

The court had ordered the police to take the driver's statement in the presence of a lawyer. The statement added it did not order his detention.

Secretary of state for transport Rafael Catala hinted excessive speed could have caused the accident.

"The tragedy that happened in Santiago de Compostela seems to be linked to excessive speed, but we are still waiting on the judicial investigation and the one carried out by the investigation commission from our own ministry," Catala said.

The national train operator said it is too early to determine the exact cause.

Prime Minister Mariano Rajoy has initiated two probes into the derailment. Three days of mourning has been declared in Spain.

Dozens of injured people remain in hospital and several of them are said to be in a critical condition.

Spanish King Juan Carlos visited the area and met the survivors. He said: "All Spanish people join in the sorrow of the relatives of the deceased."