(CNN) Thirty-seven people have been killed in a Manila casino, following an attack in the early hours of Friday morning by a lone gunman who fired shots from an assault rifle and set fire to gambling tables.

The victims, who did not appear to have been shot, are thought to have died of suffocation, Southern Police District Director Superintendent Tomas Apolinario said Friday. "Most of the victims were women who were found dead inside the bathroom," he added.

Despite ongoing ISIS-affiliated militant activity in the southern Philippines island of Mindanao, authorities ruled out terrorism as the motive for the attack. However, late Friday, ISIS claimed responsibility in a statement from its Amaq media wing , which said "Islamic State fighters" carried out the attack.

Earlier, authorities said 35 bodies were found in the casino area in Resorts World Manila after a lone gunman fired shots and set fire to gambling tables in the early hours of Friday morning.

Police told CNN Philippines that another two bodies were found in the hotel, although it was not mentioned whether these were hotel guests or employees

Thick smoke from fires set by the suspect delayed a search of the building, but officers later discovered them during clearing operations, National Capital Region Police Office (NCRPO) Director Oscar Albayalde said.

All of the bodies were found in Resort World Manila's casino area, he said. Of those killed, more than 20 were resort guests and 13 were staff. More than 70 people were injured. The gunman later killed himself.

Manila police chief Oscar Albayalde told reporters that police think it's likely the suspect was a foreigner. "He looks Caucasian, he talks English, he's big and he's white, so he's probably a foreigner," he said.

How the attack unfolded

The armed suspect forced his way into the Resorts World Manila (RWM), an upmarket hotel and casino complex near the Ninoy Aquino International Airport, around midnight local time (Thursday ET).

According to security footage viewed by police, the gunman entered via the parking lot. Police later searched a car and found registration information which they haven't made public.

The attacker walked straight into the building, past a lone security guard who panicked when she saw the suspect's automatic rifle, Albayalde said.

Reilly said only guards on the complex's perimeter are armed. Internal security officers don't carry weapons, and didn't try to engage the suspect, fearing escalation of the situation, he said.

Video of the scenes showed guests frantically running for the exits, the sound of gunshots and smoke coming from the upper floors of buildings.

Photos: Shooting at Philippines resort Relatives of a victim sit in front of the Resorts World Hotel, a popular tourist site in Manila, the capital of the Philippines that was on lockdown after a shooting on June 2, 2017. A police official said the incident was a robbery attempt by one person and not a terrorist attack. Hide Caption 1 of 10 Photos: Shooting at Philippines resort Firemen break a glass window of the Resorts World Hotel following the assault. Hide Caption 2 of 10 Photos: Shooting at Philippines resort Firemen arrive at the Resorts World Hotel. Hide Caption 3 of 10 Photos: Shooting at Philippines resort A police officer stands guard outside the resort. Hide Caption 4 of 10 Photos: Shooting at Philippines resort Smoke rises from the resort complex, which has an array of hotels, restaurants and bars. Hide Caption 5 of 10 Photos: Shooting at Philippines resort Police take positions outside the resort. Hide Caption 6 of 10 Photos: Shooting at Philippines resort A victim is stretchered away from the scene. Hide Caption 7 of 10 Photos: Shooting at Philippines resort It was not immediately clear how many people were hurt in the attack, which started around midnight on Thursday, June 1. Stephen Reilly, the resort's chief operating officer, later told reporters that about 30 people were hurt and nobody was killed, CNN Philippines reported. Hide Caption 8 of 10 Photos: Shooting at Philippines resort A victim is helped at the resort. Hide Caption 9 of 10 Photos: Shooting at Philippines resort Emergency responders tend to a victim. Hide Caption 10 of 10

The man ransacked a room and stole gaming chips, Philippines National Police Chief Ronald Dela Rosa said early Friday. He had stuffed chips totaling 113 million pesos ($2.3 million) in a backpack, but this had been recovered by police, he added.

Apolinario confirmed that during the incident the gunman had engaged in a "firefight" with casino employees.

Stephen Reilly, the resort's Chief Operating Officer, said the attacker was shot and wounded by security guards, and retreated into the hotel room where he doused a bed he was lying on in gasoline and shot himself.

"We would like to extend our gratitude to our security team," Reilly said.

"He had taken his own life by setting himself on fire followed by a self-inflicted gunshot wound," the statement said. Police confirmed he had died in a room on the fifth floor of the complex's hotel.

CNN Philippines reported he was found in the room, burned beyond recognition, next to an automatic weapon and a .380 caliber pistol.

Emergency responders tend to a victim Friday at the Resorts World Manila.

Witness: 'I could smell some kind of smoke'

Hundreds of guests and employees rushed out of the resort hotel after the gunman began shooting on the second floor, hotel employees fleeing the scene told CNN Philippines.

Jay Dones, a witness on the scene, said some employees had told him a gunman fired shots in the air.

"One of the employees told me that the suspect began pouring the contents of the bottle on one of the tables and lit it on fire," Dones said.

Witnesses also told about hearing what sounded like explosions.

"I could smell some kind of smoke that came from an explosive device," said Tikos Low, who said he was in the resort's casino along with a few hundred other people when the attack began.

The resort was put on lockdown and heavily armed SWAT officers wearing bulletproof vests and body armor descended on the scene.

The gunman didn't appear to be firing at people, said PNP Chief Dela Rosa.

Soldiers stand in front of the Resorts World Hotel following an attack in Manila on June 2, 2017.

Airport locked down

All terminals at Ninoy Aquino International Airport were placed on lockdown because of the attack, according to Robert Echano with airport operations. The airport is about a mile away from the resort.

Later the airport returned to normal operations but was on heightened alert, an airport official said.

Security remains on "high alert" status, a statement from the airport said.

In Quezon City, one of the municipalities in metro Manila, Police District Director Guillermo Eleazar ordered all 12 police stations in the city to set up checkpoints and to maximize police visibility.