A suicide bombing “cannot be ruled out” in the Peshawar mosque explosion that killed at least 93 people and wounded over 150, an initial report said on Tuesday, a day after officials told reporters that a suicide bomber had blown himself up in the mosque.

The preliminary investigation report by the police, however, was less categorical about the presence of a suicide bomber at the mosque.

Police have found “a severe head “ from inside the debris, the report said but added that some of the factors were still being evaluated before a final statement on the nature of the blast could be issued.

“The use of explosives in the incident has been confirmed, while other factors are being evaluated to confirm the nature of the blast. The investigation by teams is under way,” it said.

The explosion blew away a part of the mosque and many people were buried under the rubble.

The bombing occurred at 1:05pm on Monday, according to the report, which said that the prayer hall of the mosque has a capacity of 300 to 350 worshipers.

The initial findings have been submitted to Prime Minister Shehbaz Sharif, who along with Chief of Army Staff General Asim Munir and federal cabinet members, visited the Lady Reading Hospital to meet the survivors.

The mosque, which was named after former Peshawar police chief Malik Saad, who died in a terror attack in 2007, is located in a highly fortified area in Peshawar. It is home to the Headquarters of Capital City Police (CCPO), Frontier Reserve Police, Elite Police Force, Counter Terrorism Department, Telecommunication Branch, RRF, and SCU.

“Rescue operation is still under way with the help of Pakistan Army and Rescue 1122, for the retrieval of other casualties.”

No one has yet claimed responsibility for the blast, which ripped through the main hall. Social media is rife with the outlawed Tehreek-e-Taliban statement, distancing itself from the bombing. But, two members of the banned group earlier claimed the responsibility.

The explosion brought down a section of the roof, trapping dozens of worshippers in the rubble. TV footage showed rescuers cutting through the collapsed rooftop to make their way down and tend to victims caught in the wreckage.

“We can’t say how many are still under it,” said KP Governor Haji Ghulam Ali on his visit to the LRH hospital.

Witnesses described chaotic scenes as the police and the rescuers scrambled to rush the wounded to hospitals.

There were at least 260 people inside, a police official Sikandar Khan told Reuters on Monday.

When asked about any failure in the high-security zone, Peshawar CPO Aijaz Khan said that it looked like a “security lapse”, however, a “clear position” would be known after the investigation.