GUWAHATI, India -- Hundreds of people were feared dead when two passenger trains collided head on Monday at a railway station in eastern India, in one of the country's worst train disasters. "Some of our men who returned from the site said the death toll could be as high as 500," said an officer with the border security force helping with relief operations.

As many as 1,000 people were injured, of which more than 100 were said to be in a critical condition. Railway officials, who put the toll at 210 confirmed dead, said initial investigations suggested a signals failure was responsible for the collision. Earlier reports had suggested the crash was caused by a bomb blast. The collision took place at around 2:00 a.m.

(2030 GMT Sunday) when the Delhi-bound Brahmaputra mail smashed into the Abodh-Assam express at Gaisal, 80 kilometers (50 miles) southwest of Jalpaiguri on the state border of west Bengal and Assam. United News of India reported at least 250 passengers dead and more than 200 injured. Press Trust of India said as many as 500 people may have been killed and more than 1,000 injured in the twisted carriages of the two trains.

Officials at the railway headquarters in Gauhati said a fire englufed several coaches, burning to death some of the 2,500 passengers aboard the two trains. All four of the engineers from the trains were killed, news agencies reported. Doctors at Sadar Hospital in the nearby town of Kishanganj, which was receiving many of the injured, also indicated the death toll was far higher than the official figure.

"The reports we are getting from the site and some of the survivors suggest a toll in the area of 500," said Dr. R. Jaiswal, adding that teams of medical students had gone to the site to provide basic first-aid. District sub-divisional magistrate Samir Bannerjee, who was helping coordinate relief operations at Gaisal, said rescue teams were having difficulty cutting through the wreckage to retrieve the bodies.

"The trains were on the same track, probably due to a signals failure," Bannerjee said. "The station staff at Gaisal said they heard an explosion, but it seems this was actually the sound of the initial contact between the two trains. "The two engines and the first three or four carriages of both trains were horribly mangled together, and it's going to take some time to cut through and confirm the final death toll," he said.

The injured were being taken to hospitals in nearby Kishanganj and Islampur. Railway Minister Nitish Kumar arrived at the site Monday afternoon to oversee the rescue operations. Defense Ministry Spokesman Lieutenant Colonel Surtikant, denied reports that one of the trains might have been carrying military explosives. "We never, repeat never, transport explosives by passenger train," Surtikant said. Kishanganj district magistrate R.S.B. Singh, who visited the site, described a scene of utter carnage.

"At least 10 of the carriages were completely burned out, and it seems that many of the passengers were burned alive," Singh said. "There were body parts strewn everywhere, and the trains are so badly mangled together that there could be hundreds of bodies still trapped inside," he added. The earlier reports of a bomb blast had pointed to the possible involvement of separatist militants fighting for autonomy in northeast India.