The news yesterday evening that police had found damage to the track five kilometres south of Eschede prompted a fresh wave of speculation about the cause of the crash.
Three teams of investigators have started sifting through the evidence; but it may be weeks before they establish exactly what happened to the Inter City Express on Wednesday morning.
Early reports focused on the presence of a car near the crash site. It was suggested that the car may have been involved in a road accident on the bridge above the track and that it had fallen onto the train, causing the crash.
But police and railway officials soon ruled out this theory, adding that the car was almost certainly beside the rail track, rather than above it.
The most unusual feature of the crash was the fact that the train split in two, with the engine and the front carriages escaping the accident completely.
The driver survived without injuries and in his only statement until now, he said he felt a jolt as the train passed under the bridge. At the same time he received the emergency stop signal and braked. The engine was two kilometres beyond the crash site when it stopped.
Two rail workers were working near the track at the time of the crash. Both were killed; but officials insist that the workers were certainly not responsible for the accident. They were carrying out routine electrical checks to the switching signal at the bridge.
By yesterday afternoon it was increasingly clear that the crash was caused either by a problem on the track or a fault in the train itself.
The damaged track was just over five kilometres from Eschede, a distance it would take the train two minutes to travel.
Some survivors reported a rumbling and vibrating about two minutes before the crash.
So did the damaged track derail the train? Or was the track damaged by a faulty wheel on the train?
The hypothesis gathering momentum last night was that the fifth carriage of the train became derailed two minutes before the crash; this caused the rumbling heard by some passengers, but did not affect the whole train until the ICE approached the switching signal at the bridge.
According to this theory, the engine and the first four carriages sped beneath the bridge without difficulty; but the fifth slightly derailed carriage left the track and crashed into a pillar at the side of the bridge.
This created the concertina effect that caused the remaining carriages to pile into one another.
The first three carriages derailed but also passed under the bridge with little damage.
The carnage only started with the fourth carriage, which was hurled off the tracks and into a nearby copse by the force of the impact.
Subsequent carriages were either largely destroyed on impact with the bridge or jack-knifed against each other.
Germany's rail supervisory authority, the Federal Railways Agency, immediately pulled the train's journey data recorder from the wreckage.
Statements from survivors that there was evidence of problems before the crash have led to speculation of a fault with the train.
The German rail company, Deutsche Bahn, said yesterday it would submit all its high-speed ICE trains to safety checks.
It added that it would impose a temporary 160 kilometre (100 mile) an hour speed limit on the trains, which can reach 280 kilometres (175 miles) an hour). As the investigations into the crash continue, Deutsche Bahn is under mounting pressure to find an answer to the questions on everyone's lips: why did it happen and could it have been prevented.