A passenger train in India struck a herd of elephants as it sped down the tracks at 50 mph, killing at least six elephants and seriously injuring 10 others. Indian officials say the incident is the worst of its kind in recent memory.

No human injuries were reported in the train crash, which took place Wednesday at dusk in the Chapramari wildlife sanctuary near the Jalpaiguri district of West Bengal, India's fourth most populous state.

The Associated Press reported seven elephants, including two calves, were killed in the crash, though other Indian media report six elephants were killed.

Forest Minister Hiten Barman told news outlet The Hindu that the train was traveling faster than law allowed.

"The incident is a result of callousness on the part of the Railways. There is a clear restriction on speed, not exceeding 40 kmph [25 mph]. But we have reports that the Guwahati-bound Kabiguru Express was running at a higher speed," Barman said, adding that his office has "repeatedly urged" the railway department not to allow trains to use the 165 km of track between Siliguri and Alipurduar because the region is a popular elephant habitat.

At the time of the crash, a herd of about 40 elephants were crossing the tracks, according to the Times of India, which published news of the accident Wednesday night in India. At the time, the elephant's corpses had yet to be removed from the tracks and a relief train was reportedly dispatched to pick up stranded passengers on the disabled train.

The Times said seven elephants were crossing the tracks when the train hit them. One of the pachyderms was reportedly dragged for more than 400 meters before the train stopped.

This is not the first incident of its kind in West Bengal state. At least 50 of the mammals have been killed by trains in West Bengal since 2004, the AP reported, citing Animesh Basu, a wildlife activist and coordinator of the Himalayan Nature and Adventure Foundation.

"It is an irony that elephants are being killed by speeding trains in north Bengal on regular intervals, even though it has been declared as the heritage animal in India and an elephant calf is the mascot of Indian Railways," Basu told the AP.