It is still not clear what caused the multi-train collision, which has been described as India’s worst rail accident this century.

Indian Prime Minister Narendra Modi said Saturday that people found “guilty” over the deadly train crash that occurred in the eastern state of Odisha will receive the “harshest punishment”.

At least 288 people were killed and more than 850 injured during Friday’s incident involving two passenger trains and a goods train in the Balasore district of the state.

Rescue efforts have concluded, with officials saying all trapped and injured passengers have been retrieved.

Modi, who visited the scene Saturday and talked to rescue workers, called the incident a “painful” one and also pledged to look after the families of those killed and injured in the accident.

“This is a very big, painful, and disturbing incident. Those family members who have been injured, the government will leave no effort for their well-being,” he told reporters.

“Those we have lost will not come back, the government is with the families in hour of grief. It’s a very serious matter of concern for the government. Instructions have been given for all types of inquiries and the guilty should get the harshest punishment, they will not be spared.”

It is still not clear what caused the multi-train collision, which has been described as India’s worst rail accident this century. A full investigation has been launched, but a preliminary report indicates the accident was caused by signal failure.

KS Anand, chief public relations officer of the South Eastern Railway, said: “The Coromandel Express was supposed to travel on the main line, but a signal was given for the loop line instead, and the train rammed into a goods train already parked over there. Its coaches then fell onto the tracks on either side, also derailing the Howrah Superfast Express.”

Some 2,000 passengers are thought to have been aboard the two passenger trains involved. Many dead bodies remain in the wreckage of the trains, and the death toll is expected to continue rising.

Modi also met with survivors in hospitals. He said: [I] took stock of the situation at the site of the tragedy in Odisha. Words can’t capture my deep sorrow. We stand committed to providing all possible assistance to those affected.”

Families of the dead will receive 1 million rupees ($12,000), while the seriously injured will get 200,000 rupees, with 50,000 rupees for minor injuries, railway minister Ashwini Vaishnaw said. Some state governments have also announced compensation.

India has one of the largest train networks in the world with millions of passengers using it daily, but a lot of the railway infrastructure needs improving.

Modi’s administration launched high-speed trains as part of plans to modernise the network, but critics say it has not focused enough on safety and upgrading aging infrastructure.