Rescuers took nearly five hours to get to the scene of the disaster. Many of the injured were only freed in the late afternoon, and were given emergency aid at the scene. The crash happened at 4.30am. The train was heading for the coastal city of Mombasa.
Police Commissioner Phelemon Abongo confirmed the death-toll and said that at least 100 people were injured.
He added that some 645 people were on the overcrowded train, with many of them standing in economy-class carriages.
Air force personnel who were in charge of the rescue operation took the most serious casualties to Nairobi. They said that more than 50 people had been taken to hospitals on the coast.
They described the accident as horrific. Most of the those killed had been in the third-class carriage. First and second-class carriages near the front of the train overturned, trapping and killing some of the holidaymakers.
The first military plane to arrive in Nairobi yesterday carried a French tourist, Beatrice Perez, who called the disaster "ten hours of hell".
She had been trapped in the first-class carriage with broken legs. Arriving with some 30 of the most seriously injured passengers, she was taken to Nairobi Hospital in one of a fleet of ambulances on standby all day at the airport.
Ms Perez, who lives in London, had booked her holidaywith the British- based Abercrombie and Kent, the tourist company which this month had to close its camp in Bwindi Park, Uganda, after eight tourists were murdered by Rwandan rebels.
"The train was going very fast, too fast, then the middle of the train swung one way and we came off the tracks. I would say it was human error," she said.
A member of a group of French tourists, Pascal Lepailler, 29, described how one of his female travelling companions was killed by the impact of the crash. He remained trapped in the carriage with the body while others lit a fire outside in an area notorious for lions - "some made a fire because of the animals, some tried to help the injured, while others walked about five kilometres to telephone for help".
The train crashed at a junction called Maneaters, which is named after the lions that preyed on railway-builders a hundred years ago.
The British High Commission said all 11 of its nationals on the train had been confirmed to be safe, although some sustained injuries. Consul James Dunlop flew to the scene in a chartered aircraft early in the afternoon.
Kenyan emergency services included the Flying Doctor team, the Kenyan Wildlife Services, the Kenyan Red Cross and St John's Ambulance personnel, who helped to transport people with spinal, head and limb injuries.
The railway is frequently used to take traders, travellers and tourists to the coast.
It was built nearly a century ago by the British colonial authorities. It has seen little modification, and recently suffered serious financial problems; there have been plans to privatise it.
Many sections were damaged by floods last year, and the line was considered to have been in need of repair.