The 'A' line of Rome's metro system was back to normal Wednesday morning, less than 24 hours after the train crash which killed one person and injured over 200, five of them critically.
But the reasons why one train smashed into the back of another, while it was letting passengers get off at the Piazza Vittorio station, remained mysterious.
The cause of the accident "has still to be pinpointed", Transport Minister Alessandro Bianchi told parliament on Tuesday night, adding: "We can't rule anything out".
Bianchi stressed in his report to MPs that the security systems installed on the two new trains were the best on the market. They have three braking systems, two of which should
activate automatically in danger situations.
Rome prosecutors have begun an investigation into the accident and the government has set up a commission of enquiry to establish the causes.
Technical experts from the Spanish company which supplied the trains were helping to examine the wreckage for clues to the dynamics of the collision. Police and experts sifted through the wrecked train compartments through the night, filming and cataloguing thousands of pieces of
evidence.
The 'black box' recorders from the two trains have been recovered and experts were expected to begin studying them shortly. A crucial detail recorded by the black boxes was the speed of the second train on impact.
This is thought to be one of the keys to understanding what happened.
Taking into account that the moving train entered three metres inside the stationary one, the transport ministry's experts believe the oncoming one was going at 25-30 km/h.
The Rome metro company said it was travelling at 15km/h.
DRIVER TOLD TO IGNORE RED LIGHT.
The moving train went through a red light, after being given permission to do so by the metro system's central control room. This order, which is not uncommon during peak periods, was given in order to space out the trains on the line.
The driver of the second train, Angelo Tomei, survived the crash and has confirmed going through a red light.
He said he was going slowly, as is laid down in the rules for this sort of situation, when drivers must rely on their own vision and in any case not exceed 15 km/h.
Tomei has reportedly told investigators that he noticed something was wrong a few minutes before impact. According to one newspaper report, he said he heard a loud noise and
noticed a burning smell.
Some underground train drivers were reported as saying there had recently been problems with the brake system on the train being driven by Tomei.
The driver was questioned on Wednesday by prosecutors who are trying to establish whether there is any evidence to support possible accusations of manslaughter or criminal responsibility in the crash.
Tomei's name has been written in the list of suspects but only for technical reasons as he is not accused of any crime at present.
