The incident occurred at 6.15 am near Motichoor Fatak under Raiwala police station, about 50 kms from Dehradun, when a group of eight elephants abruptly came on the tracks, SHO Manoj Singh Negi said.
By the time the train came to a halt, it had hit two elephants, killing one on the spot and leaving another injured, he said.
The rest of the elephants fled into the nearby forests, he said.
The incident disrupted rail traffic on the route for nearly four hours as it was difficult to pull the huge pachyderm from between the tracks and the engine, he said.
The driver of the train told police that the elephants came suddenly in sight and it took the speeding train a while to come to a halt.
The train was going at high speed and it must have gone about a 100 metres before coming to a halt after the brakes were applied, the official said quoting the driver.
Environment Minister Jayanthi Natarajan had recently accused the Railway Ministry of remaining "indifferent" to the death of wild animals particularly elephants caused by speeding trains.
In a letter to Railway Minister Pawan Bansal, Natarajan said, "Despite repeated pleas, railway authorities remain indifferent to the death of wild animals particularly elephants caused by speeding trains."
On December 30, six elephants were mowed down by Coromandel Express in Odisha's Ganjam district.