The incident took place around 5.45 p.m. Wednesday near the Nagrakata-Jaldhaka bridge in West Bengal's Jalpaiguri district.
An earlier report said six elephants were killed, but authorities later revised the figure to five.
State Forest Minister Hiten Burman and wildlife officials alleged that the train was travelling at a speed far higher than the limit prescribed for the area, which is part of an elephant corridor.
The forest and wildlife departments have initiated a joint probe into the incident.
The railways, however, denied that the area was part of an elephant corridor.
After the accident, officials said as many as 15 elephants may have been injured in the incident. A team along with three trained elephants has been sent to the forest to locate the wounded animals prior to treating them for injuries.
A total of 43 elephants have been killed by speeding trains in Dooars forest in recent months.
--IANS (Posted on 14-11-2013)