BHUBANESWAR, June 3 (Reuters) - At least 233 people were killed and 900 were injured when two passenger trains collided in India’s Odisha state, a government official said on Saturday, making the rail accident the country’s deadliest in more than a decade.

The death toll is expected to increase, state Chief Secretary Pradeep Jena said in a tweet.

He added that over 200 ambulances had been called to the scene of the accident in eastern state Odisha’s Balasore district and 100 additional doctors, on top of 80 already there, had been mobilised.

Images from the scene showed rescuers climbing up the mangled wreck of one of the trains to find survivors, while passengers called for help and sobbed next to the wreckage.

Early on Saturday morning, video footage showed police officials moving bodies covered in white cloths off the railway tracks.

Videos shared on social media showed the arrival of several ambulances and people being pulled out of the upturned train coaches.

“I was there at the site and I can see blood, broken limbs and people dying around me,” an eyewitness told Reuters by phone.

An extensive search-and-rescue operation has been mounted, involving hundreds of fire department personnel, police officers and sniffer dogs. National Disaster Response Force teams were also at the site.

Hundreds of young people lined up outside a government hospital in Odisha’s Soro to donate blood.

The collision occurred at about 7pm local time (9.30pm, Singapore time) on Friday when the Coromandel Express, which runs from Kolkata to Chennai, collided with another passenger train, the Howrah Superfast Express, which runs from Bangalore to Howrah.

Authorities have provided conflicting accounts on which train derailed first to become entangled with the other and have yet to make any statements about possible causes.

Although Chief Secretary Jena and some media reports have suggested a freight train was also involved in the crash, railway authorities have yet to comment on that possibility.

Odisha Chief Minister Naveen Patnaik said authorities’ priority was “removing the living to the hospitals, that’s our first concern, to look after the living”.

Rescue operations were underway at the site and “all possible assistance” is being given to those affected, Prime Minister Narendra Modi said in a tweet.

Rescue teams have been mobilised from Odisha’s Bhubaneswar and Kolkata in West Bengal, federal Minister for Railways Ashwini Vaishnaw said in a tweet.

According to Indian Railways, its network facilitates the transportation of over 13 million people every day. But the state-run monopoly has had a patchy safety record because of ageing infrastructure.

Odisha’s Chief Minister Naveen Patnaik declared a day of state mourning on June 3 as a mark of respect to the victims.