A Central Industrial Security Force, or CISF, trooper who worked as a nuclear plant guard has shot and killed three of his colleagues in the southern Indian state of Tamil Nadu, according to local media reports. The shooting spree at the CISF base near the Kalpakkam nuclear plant also reportedly injured two other security personnel.

Police reportedly said that the incident, which occurred in the morning, took place about six miles from the nuclear power plant, but the reason for the attack was not yet known. Authorities reportedly said that the bodies of the deceased were taken to a government hospital for autopsy, while those injured were being treated. According to reports, there were at least 50 other security personnel at the base when the shooting took place.

“They had assembled for morning duty when he opened fire,” CISF spokesperson Hemendra Singh told Agence France-Presse, The Express Tribune reported. “We are looking into the matter and checking what triggered this. But we immediately detained him and handed him over to the police.”

The shooter has been identified as head constable Vijay Pratap Singh, according to The Times of India.

A CISF spokesman said that Singh had been working for the organization for 24 years and was recently posted to Kalpakkam, from Narora in the northern Indian state of Uttar Pradesh, The New Indian Express reported.

Operations at the nuclear plant have not been affected, a spokeswoman for the Indira Gandhi Centre for Atomic Research reportedly said.

“The incident happened at the extreme corner of the township inside the barracks,” she reportedly said.

Top security officials from the Department of Atomic Energy in the city of Mumbai are travelling to Tamil Nadu to investigate the case, The New Indian Express reported.