A massive explosion struck a night market in Davao City, hometown of Philippines President Rodrigo Duterte, on Friday night (local time). At least 15 people have been reportedly killed, with more than 60 wounded.

CNN relayed word from Philippine police that 10 people died at the scene, while others died after being taken to the Southern Philippines Medical Center for treatment of their injuries.

“The blast struck outside a high-end hotel at a busy market in Davao City on the southern Philippine island of Mindanao at around 10.15pm local time on Friday,” the Daily Star reports. “Buildings near the market, including a university, were lockdown for hours.”

The Daily Star says it is “unclear what caused the jolt, but a bomb has not been ruled out,” noting that the national police force just thwarted an assassination plot against President Duterte, “who usually flies home to Davao City every weekend.”

However, the regional police chief superintendent, Manuel Gaerlan, declared the government is on guard “in case there are other attacks,” which would suggest the authorities believe the explosion was created deliberately.

Duterte’s son Paolo is the vice mayor of Davao City. He was evidently unharmed in the explosion, as he was available to report at least 60 casualties to the media and promised “a thorough investigation is being conducted to determine the cause of the explosion,” per the BBC.

If it was a bomb attack, there are two prime suspects: the drug cartels Duterte has been vigorously at war with, and Abu Sayyaf, an Islamist group that was supposedly inching toward a cease-fire with the government, but in recent days has talked about waging “jihad” and a “last war, to the finish” with over a thousand fighters.

Late Friday afternoon, GMA News Online reported that the Philippine Department of National Defense has “pointed to the Abu Sayyaf group as the perpetrator of the deadly explosion” in Davao City.

Defense Secretary Delfin Lorenzana announced that his forces were on high alert, “especially in urban centers for possible other terroristic act attempts by this group.”