At least 40 passengers were killed when a bus plunged into a canal in the central Indian state of Madhya Pradesh on Tuesday, police told AFP as recovery efforts continued.

The accident happened when the bus, which was carrying more than 50 passengers, veered off the road and into the water near the village of Satna early on Tuesday morning.

It was unclear what caused the bus to swerve, but India's vast network of roads is poorly maintained and notoriously dangerous.

Local media reported the bus was completely submerged, and images showed officials in orange life jackets using rescue boats to look for survivors. 

According to media reports, seven people, including the driver, managed to swim to safety. 

"We have so far found 40 bodies and they have been sent for autopsy. Search and rescue operations are underway," said district police superintendent Dharamveer Singh.

The state government has ordered an inquiry into the accident. 

An initial investigation suggested the driver lost control of the bus, reports said. The bus then hit a bridge before crashing into the water.

Local officials stopped the release of water into the canal, which sped up the rescue operations and allowed two cranes to pull the bus out, reports said. 

The Times of India newspaper quoted sources saying it took three hours to lift the vehicle out.

Prime Minister Narendra Modi's office tweeted that the families of those killed would receive 200,000 rupees ($2,750) in compensation.

"The entire state is standing with those affected," Madhya Pradesh chief minister Shivraj Singh Chouhan said in a video message.

High-speed vehicles jostling with motorbikes, pedestrians and cyclists combine with poor infrastructure and poorly maintained vehicles to make India's roads treacherous.

In 2019 more than 150,000 people died -- 410 every day or 17 an hour -- in almost half a million accidents, according to the government.

The United States sees nearly five times more accidents than India every year but the number of deaths in India is four times higher, according to the Times of India.

The main causes are excessive speed, not wearing helmets -- sales of two-wheelers far outstrip those of cars -- and not using seatbelts.

Earlier this month, Transport Minister Nitin Gadkari inaugurated Road Safety Month, saying that the government aimed to halve road deaths and accidents by 2025.

In the same month an out-of-control dumper truck crushed fifteen people to death as they slept by the roadside in the western state of Gujarat.

The dead included a baby girl, eight women and six men. The truck collided with a tractor carrying sugarcane just after midnight at a crossroads.