NEW DELHI, Dec. 23 (Xinhua) -- At least 27 people have been killed and over 20 others injured after a passenger bus veered off a bridge and plunged into a river in the northern Indian state of Rajasthan Saturday, police said.

The accident occurred in Dubi area in the state's Sawai Madhopur district, some 150 km from Rajasthan's capital Jaipur.

"The bus ferrying over 50 pilgrims broke the railing of a bridge and fell into Banas river after the driver lost control of the speeding bus following a tyre burst. The driver was at the time trying to overtake another vehicle on the narrow bridge," a senior police official said.

While 27 bodies have been fished out of the river, those injured have been admitted to a local hospital, he said. "The death toll may go up as some other passengers are still feared missing after they drowned in the river," the official added.

Indian Prime Minister Narendra Modi has condoled the deaths. "My thoughts are with the families of the deceased. State government is closely monitoring the situation, including rescue operations, and providing all possible assistance to those affected," he tweeted.

Local TV channels reported that the bus which was carrying over 50 people, all on a pilgrimage from Sawai Madhopur to Lalsot, had been allegedly driven by its minor conductor while the driver was taking a rest.

"The district's administrative head Kailash Chand Verma and local police chief Maman Singh are monitoring rescue operations at the spot. The wreckage of the bus has, however, been pulled out of the river using a crane," the official said.

A probe has been ordered into the incident, he said, adding that strict action would be taken against the bus owner if reports of the minor being on the driver seat at the time of the accident turned out to be true.

India has one of the highest number of road fatalities in the world. Road accidents occur mostly due to poor driving or badly maintained roads and vehicles.