Search teams today located one black box from the wreckage around two trains that crashed into each other near Brussels, killing 18 people and injuring more than 170.
One train driver survived the crash with serious injuries but he was not well enough to be questioned, railway officials said.
The Eurostar and Thalys high-speed trains from London and Paris to Brussels said they were suspending services for a third day on Wednesday and other train drivers held a wildcat strike today that left thousands of commuters without their normal transport.
Rescue workers picked through the wreckage of the two commuter trains that collided on Monday in one of the deadliest rail accidents in Belgian history. Provincial officials raised the number of injured from 95 to 171 people, some seriously hurt.
European Commission officials said the rail track near the Buizingen station where the crash took place, nine miles south of Brussels, lacked the latest automatic braking system designed to stop trains after they pass through a red signal.
Lodewijk De Witte, the governor of the province of Flemish Brabant, had said earlier that one train apparently did not heed a red signal as the second train - leaving 10 minutes late from Buizingen - moved on to the track of the oncoming train.
National Railways spokesman Jochen Goovaerts described the wreck as a lateral collision, contradicting initial reports that the trains crashed head-on. One train was apparently diverting to another track when it was hit by the second.
The search continued for the second data recorder that could help determine whether mechanical failure, human error, freezing weather or another factor was primarily responsible for the crash. They should also reveal how fast the trains were moving when they collided, said Mr Goovaerts.
"There are a lot of possible explanations to this tragedy," he said. "We don't want to put the blame where it doesn't belong."
The accident scene was sealed off today with police tape. One passenger car from each train was tipped on to its side, and it was unknown whether more bodies were trapped underneath.
Mr Goovaerts said the surviving driver was on the train that was approaching the station.
Infrabel, the rail management company, said its technical teams would need three days to inspect six rail lines once the wreckage is removed, meaning train traffic was likely to remain disrupted in the capital for the rest of the week.
Meanwhile, a wildcat strike by about half of Belgium's train drivers paralysed much of the traffic in the southern part of the country and caused cancellations and delays in the north.
"It was an emotional reaction to the catastrophe of yesterday," Mr Goovaerts said, explaining that many railway employees were outraged at accusations blaming one of the drivers for the accident before an investigation was completed.
Infrabel called for the installation of automatic braking systems on all trains. Officials said these would have prevented the accident by immediately activating the brakes on the train that allegedly ran the red light at the entrance to the station.
The collision appeared to be the country's worst train crash since 1954, when a collision near Leuven killed 20 German football fans and seriously injured 40 others.
Europe's worst recent crash occurred near the German town of Eschede in 1998 when around 100 people were killed when a cracked wheel hurled a train off the tracks.
Belgium is ranked 12th in the 27-nation European Union for rail safety, according to EU statistics. Estonia, Lithuania and Slovakia head the list of nations with the most accidents on the continent.