India’s federal crime agency said Friday it has arrested three railway officials in connection with one of the country’s deadliest train accidents, which killed more than 290 people last month.

The arrested men have been charged with culpable homicide without murder and destruction of evidence, the Central Bureau of Investigation said in a statement. It identified them as two signal engineers and one technician, and said the investigation is ongoing.

June’s train crash in eastern Odisha state occurred when a packed passenger train was mistakenly diverted onto an adjacent loop line where it rammed into a stationary freight train loaded with iron ore. The collision derailed the passenger train’s coaches onto another track where they struck a passing train that was running in the opposite direction.

The two passenger trains were carrying more than 2,290 people when the collision took place. Nearly 1,000 people were injured.

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After the accident, India’s railway minister Ashwini Vaishnaw said the cause of the crash was related to the signalling system.

India, a country of 1.42 billion people, has one of the world’s most extensive and complicated railways built during the British colonial era: more than 40,000 miles of tracks, 14,000 passenger trains and 8,000 stations. Spread across the country from the Himalayas in the north to the beaches in the south, it is also a system that is weakened by decades of mismanagement and neglect.

Despite efforts to improve safety, several hundred accidents happen every year, and most such crashes are blamed on human error or outdated signaling equipment.

The June crash was India’s deadliest since 1995, when two trains collided near New Delhi, killing 358 people. In 2016, a passenger train slid off the tracks between the cities of Indore and Patna, killing 146 people.