"But the police will not bite right away their claims because we have to establish facts here in order to come up with a conclusion", Dela Rosa said. He said investigators would check whether the sprinklers in the hotel worked. Most of the bodies were found in the casino area, BFP officials told ABS-CBN News.
It was not clear how the gunman smuggled gasoline and an assault rifle into the crowded casino or what prompted dela Rosa to cast doubt on terrorism so quickly.
The unidentified gunman opened fire at the casino resort just after midnight, according to the Philippine National Police. A South Korean died of a possible heart attack suffered during the evacuation, the country's Foreign Ministry said.
Abu Sayyaf is best known for engaging in kidnapping for ransom, occasionally abducting foreigners from vacation spots in the southern Philippines. The national police chief described him as "white, with a mustache" and about 6 feet tall.
"Our daughter called us past midnight saying she was in the VIP section of the casino and there was smoke and they were suffocating", Gil Yongco said.
People mostly minor injuries such as bruising as they stampeded to get out, according to police.
The resort said it was on "lockdown" following the attack, which it attributed to multiple assailants.
The suspect was found with a rifle, and authorities were searching his auto. Before the attack, he got out of the auto and entered the building with his rifle.
Kimberly Molitas, a spokeswoman for the capital's police office, said 113 million Philippine pesos (US$2.27 million) worth of casino chips stolen during the raid had been recovered.
Abayalde says there was no indication of terrorism. "It's either he lost in the casino and wanted to recoup his losses or he went totally nuts", Albayalde said.
He said it seemed like the gunman was focused on the gambling table and stealing chips.
Philippine Red Cross (PRC) said at least 25 people were injured and were taken to various hospitals.
Dela Rosa said the gunman apparently barged into a room on the fifth floor of the Maxims hotel connected to the mall and casino, laid on the bed, blanketed himself, doused himself with gasoline and set himself on fire, AP reported.
"It's too early to tell", he added.
The incident unfolded when the gunman forced his way into the Resorts World Manila casino, shot at gambling machines and set tables on fire.
Dela Rosa said security footage showed the gunman ignoring a guard who tried to question him at the entrance.
President Donald Trump is offering the thoughts and prayers of the American people to those impacted by an attack at a tourist resort in the Philippines.
Military spokesman Restituto Padilla said the police were in control of the situation and the army was monitoring closely. "Maybe because of the heavy firearm, they can't put up a fight so they prioritised life and safety", Jeff Santos, a high roller at Resorts World Manila, told a Philippine radio station.
Gunfire and explosions have been heard at the Resorts World Manila in the Philippines, CNN Philippines reported.
Australia warned early Friday morning that the deterioration of security in Mindanao "has resulted in a more volatile security environment in the Philippines". "Before we exited, we heard two gunshots and there was thick smoke on the ground floor".
Resorts World Manila, in the southwestern part of metropolitan Manila near Ninoy Aquino International Airport, said on Twitter early Friday that it was working closely with police to ensure the safety of employees and guests, adding, "We ask for your prayers during these hard times".