Bomb threat messages circulated the night before the fatal explosion at the Dimaporo Gymnasium of Mindanao State University in Marawi City on Sunday, the Bangsamoro government said on Monday.

In a public briefing, Bangsamoro Autonomous Region in Muslim Mindanao spokesperson Naguib Sinarimbo said the text messages about a planned explosion started circulating on Saturday night without specifying the location.

"This really needs a thorough examination to pinpoint the true origin of this bombing," Sinarimbo said.

In 2017, Marawi, the capital city of Lanao del Sur, faced a siege from militants affiliated with ISIS, causing around 1,000 casualties and becoming the Philippines' lengthiest urban conflict.

Nearly five years later, on 3 December 2023, an explosion occurred during a Catholic Mass at Marawi State University's gym, resulting in the loss of four lives and causing injuries to at least 43 people.

7 victims need major surgeries

Sinarimbo said that seven individuals are hospitalized with injuries resulting from the bombing at MSU-Marawi, adding that these individuals need surgeries.

"Based on reports we received from the data of the emergency operation center of the provincial government of Lanao del Sur and the incident command post at MSU, there are four confirmed fatalities," Sinarimbo said.

"Additionally, seven individuals still in the hospital require major surgeries," Sinarimbo added.

He also mentioned that 43 other individuals got minor injuries, adding that the regional government would cover the hospital expenses.

60mm mortar round found

In a separate press briefing at Camp Crame, the Philippine National Police said they found fragments of a 60mm mortar round at the Dimaporo Gymnasium in MSU-Marawi.

"But as for what triggered the device, whether it's battery-operated or cellphone-operated, they are still piecing together the fragments of the improvised explosive device that was used," PNP spokesperson Police Colonel Jean Fajardo said in the briefing.

There's no sign suggesting it was a suicide bombing, according to the official.

However, Fajardo said the PNP is investigating at least two individuals who might have connections to the bombing.

She mentioned that the two individuals of interest in Sunday's explosion had been connected to previous bomb attacks in different areas of Mindanao.

"Based on gathered evidence, including witness accounts, they are looking into two persons of interest. Based on the images shown, there have been positive identifications of these individuals as persons of interest," Fajardo said.

Additionally, Fajardo said officials found a bag that might have concealed the bomb.

"Authorities didn't recover any CCTV footage that might assist in identifying potential suspects, but they are gathering footage from outside MSU to aid in the ongoing investigation," Fajardo said.