More than 500 passengers are killed when their train plunges into the Bagmati River in India on June 6, 1981. The rail accident—the worst in India to that date—was believed to have been caused when an engineer tried to avoid striking a cow.

The nine-car train, filled with approximately 1,000 passengers, was traveling through the northeastern state of Bihar about 250 miles from Calcutta. Outside, monsoon-like conditions were battering the region. Extremely hard rains were swelling the rivers and making the tracks slick.

As the train approached the bridge over the Bagmati River, a cow crossed the tracks. Possibly seeking to avoid harming the cow, the engineer braked too hard. The cars slid on the wet rails and the last seven cars derailed straight into the river. With the river far above normal levels, the cars sank quickly in the murky waters.

Rescue help was hours away and, by the time it arrived, nearly 600 people had lost their lives. After a multi-day search, 286 bodies were recovered but more than 300 missing people were never found. The best estimate is that close to 600 passengers were killed by the engineer’s decision. Cows are considered sacred animals, according to the Hindu religion.