At least 20 people were killed and 17 injured when a bus fell off the Mahatma Gandhi bridge over the Ganga river in Bihar's Vaishali district early Friday morning.

The bus plunged more than 100 feet to fall on the dry riverbed near pillar number seven, about 15 km from Patna, when the driver lost control and the vehicle crashed through the railing of the bridge, officials said.

Those killed included two women and as many children, Sub-Divisional Officer B K Sinha of Hajipur, the headquarters of Vaishali district, told PTI.

The bus was on its way to Patna from Raxaul in East Champaran district, Sinha said.

Earlier reports had said the Bihar State Road Transport Corporation bus was on its way from Motihari, headquarters of East Champaran district, to the state capital.

While 18 passengers died on the spot, two more succumbed to their injuries at the Sadar Hospital in Hajipur, Sinha said.      

Eleven passengers are being treated at the same hospital while six were rushed to the Patna Medical College and Hospital in a  critical condition, he said.