SARAJEVO (Reuters) - Three people died and four were injured in an incident on Thursday caused by a gas leak in Bosnia’s Una Kostela hydropower plant, police and the plant’s operator EPBiH said.

“It was confirmed that there was a gas leak inside the facility,” a regional interior ministry spokesman told Reuters.

Bosnia’s top power utility EPBiH said in a statement that all the victims were its employees. The incident happened when they were cleaning the plant’s drainage system, it added.

The investigation into the incident was still underway.

The 13.7 megawatt (MW) Una Kostela hydropower plant is located near the northwestern town of Bihac.