ESCHEDE, Germany (CNN) -- Trained dogs helped rescuers search twisted mounds of steel early Thursday after Germany's worst rail disaster in half a century. As many as 120 people were feared dead after a high-speed passenger train derailed and slammed into a bridge when the lead locomotive broke loose.

At least four children were expected to be among the victims from Wednesday's crash. Authorities said they had retrieved 89 bodies and could see more corpses trapped in the wreckage.

The crash occurred when the Inter City Express (ICE) train, traveling 125 mph (200 km/h), derailed.

Car after car slammed into an overpass, bringing the bridge crashing down on the wreckage and victims. Just 150 feet (46 meters) away, houses were unscathed, protected by the embankment.

At least 30 people were seriously injured, and there were still two rail cars buried beneath the collapsed bridge and other wreckage the workers had not yet reached.

The Munich-to-Hamburg train, which was carrying mostly business people, was approaching the Eschede station in northern Germany when the accident happened at about 11 a.m.

The accounting of dead and injured was hampered by the severity of the mangled wreckage. Police could not confirm reports that a group of schoolchildren was still trapped in the wreckage.

A rattle and then a crash

Passengers felt a rattle just before the jarring crash, one survivor said.

"I held on and ducked down because you had the feeling you'd be thrown through the air and then, thank God, it came to a standstill," Wolf-Ruediger Schliebener, a passenger from a rear car, told SAT 1 TV.

"When I saw what had happened, I realized how lucky I had been to get out at all," he said.

The locomotive driver survived the crash because the locomotive uncoupled from the train and passed under the road bridge, rail officials said at a news conference.

Oblivious to the catastrophe behind him, the driver kept driving through the small train station at Eschede, 25 miles (40 km) north of Hanover. The station master finally hit the emergency brakes, bringing the engine to a halt more than a mile (1.6 km) from the overpass.

Federal investigators interviewed the driver, who was in shock.

"The train engineer felt a tug which automatically released the brakes, and then he looked out the window and noticed he no longer had a train behind him," investigator Gisela Luening said.

"The train split in two," added Peter Muenchschwander, a German Railways official. "The first half went under the bridge and the second half rammed the bridge, which then collapsed."

The accident was the worst in Europe since 1974, when 153 people were killed in Zagreb when a train bound for Germany from Belgrade derailed.

It was the worst in Germany since June 1945 when 102 people were killed after an American troop transport train crashed into a train carrying German war prisoners near Munich.

Shocked survivors

All the train's cars and the rear engine derailed, and splintered glass covered the scene. Luggage was piled next to the wreckage, and residents watched survivors wander away in shock.

Survivors were taken to hospitals throughout the region. The Red Cross chartered six buses to take most of the uninjured to Hamburg, spokesman Harald Krueger said.

Hundreds of people, moved by the tragedy, gathered at Red Cross stations across the country to donate blood.

The cause of Germany's worst train accident since World War II remained unclear late Wednesday. Officials were even unsure how many people were aboard Hamburg-bound ICE 884.

The account of the lead locomotive decoupling, given by chief regional rescue coordinator Klaus Rathert at a news conference, conflicted with earlier reports suggesting that an automobile had plunged into the train from the overpass.

Police said an automobile was crushed beneath the wreckage, but it was unclear where the car was parked at the time of the wreck. They said it probably was sitting along the tracks and not on the overpass.

Tangled wreckage hampers rescues

Rescue workers picked through the wreckage with a crane, and used blow torches to pry open metal siding.

"This shakes me to the core. I had to collect body parts, legs and arms of men, women and children," said fireman Walter Stroetmann, one of more than 1,000 rescuers. Among them were trauma surgeons.

Survivors were found among the tangle of metal -- including a 10-year-old girl pulled out 11 1/2 hours after the crash.

The accident brought condolences from world leaders.

Chancellor Helmut Kohl, informed of the tragedy after arriving in Italy for meetings with Premier Romano Prodi, appeared shaken by the news and cut his visit short to return to Germany.

"So many dead ... It's a tragedy," Kohl, his face tight, said in Bologna with Prodi at his side. "Excuse me, but I must return home right away."

The train belonged to the ICE class, which is the pride of German Railways and was introduced in 1991 to rival air travel. The ICE train travels up to 175 mph (280 km/h) and requires 1.7 miles (3 km) to come to an emergency stop at top speed.

The Associated Press and Reuters contributed to this report.