At least 150 prisoners at the North Cotabato District Jail in the Philippines escaped after approximately 100 gunmen attacked the facility on Wednesday morning, BBC reported. One guard was killed and one inmate was injured during the breakout. The jail is located near the city of Kidapawan on the Mindanao island.

Jail warden Peter Bonggat told reporters that the inmates “took [their] chances because of the volume of fire” between the prison guards and the gunmen. “They used their bedding, piled them on top of each other to escape,” Bonggat said, adding that he believed the assault was carried out to free several rebels who were imprisoned there. However, it was unclear whether any of the rebels had managed to escape.

Authorities said the attack was likely carried out by militants linked to separatist groups, AFP reported. Bonggat said the attackers were believed to be part of a breakaway faction of the Moro Islamic Liberation Front, the country’s biggest rebel group, which is currently in peace talks with the Philippine government. Later, a spokesperson for the group said it did not know who the attackers were.