In India’s southern state of Andhra Pradesh, two passenger trains collided on Sunday, killing at least 13 people and injuring about 50 others.

Over 100 emergency workers were on site clearing the wreckage as a rescue operation was launched.

A preliminary investigation has determined that there was a “human error” that caused the collision.

In a message to the railways minister, Prime Minister Narendra Modi expressed his condolences.

During the evening of Sunday, there was a crash in the Vizianagaram district.

As a result of a collision with another train, three carriages of a passenger train travelling between Visakhapatnam and Palasa derailed around 19:00 (13:30 GMT).

An incoming passenger train travelling between Visakhapatnam and Rayagada rammed into the stopped train from behind due to a broken overhead cable, a railway official told Reuters.

To rescue passengers and remove bodies, hundreds of ambulances, doctors, nurses, and rescue personnel were sent to the scene.

According to East Coast Railway’s Chief Public Relations Officer, Biswajit Sahu, “overshooting of signal” by the second train caused the collision.

After the accident, 33 trains were cancelled and 22 were diverted. It is expected that the affected track will be cleared by Monday evening so that traffic can resume.

The office of Andhra Pradesh’s Chief Minister YS Jagan Mohan Reddy said he would visit the accident site on Monday. In addition, the minister has announced financial compensation for the victims.

Many of the railway infrastructure in India needs to be improved since it has one of the world’s largest train networks with millions of passengers every day.