The Kenya Railways chairman, Jeremiah Musuva, said the train had been carrying 600 passengers. Hundreds of people were missing or injured in the crash, the worst since Kenya gained independence from Britain in 1963. The river's bank was littered with bodies retrieved by armed forces divers and police rescue units.
Officials said they feared tourists travelling to Nairobi could be among the dead. Mr Musuva said a Canadian and an unidentified European were among those killed. Rescuers stopped sifting through the mangled, half-submerged wreckage late last night while they waited for the Kenyan navy to bring in bright lights for night work. Earlier, military, police and railway security teams used power saws and axes to cut through coaches to retrieve trapped bodies.
Mr Musuva said a ticket inspector on the train had pulled an emergency cord to release third class coaches from the rest of the train, saving many passengers. Several tourists normally travel in first and second class.
'It appears the train was forced off course by the floods, hit the bridge and crashed into the river Ndethia Geithia. Five other coaches followed,' a rescue team leader said. Ndethia Geithia literally translates as God Save Us. The accident spot is in uninhabited shrubland four miles from the main Mombasa-Nairobi road.
Mr Musuva said the floods had also swept away the railway's communication system, making it difficult to report the accident.
The bridge, on the main rail route from the resort of Mombasa to the Lake Victoria port of Kisumu, was eroded by the raging flash floods and collapsed under the weight of the train's head and first coaches. Witnesses said coaches had been washed at least 500 yards from the bridge.
The Police Commissioner, Philip Kilonzo, said rescue efforts would continue for at least two days before a final death toll could be established.
The Transport and Communications Minister, Dalmas Otieno, said the bridge which was swept away in the crash was built in 1898 and had received very few repairs since then.