Thirteen people facing drug charges escaped from a police detention facility in the Philippines today after sawing through iron bars, the Philippine Drug Enforcement Agency (PDEA) said.

The guard on duty at the facility north of the capital Manila is now under investigation, said PDEA regional director Juvenal Azurin.

"We are also trying to find out how they were able to bring in an iron saw inside the facility," Azurin told reporters, adding that most of the detainees were from nearby Bulacan province and were recently arrested for selling crystal methamphetamine.

Philippine President Rodrigo Duterte has made the PDEA the country's main anti-drug agency after last month suspending police operations in the country's narcotics crackdown after a South Korean businessman died north of Manila in October.

The army has also been called in to support the 1,800-member PDEA nationwide.

More than 7,700 people have died in Duterte's war on drugs since he came to power on June 30. About 2,500 were killed during police raids and sting operations when suspects chose to resist arrest.