Investigators probing the aftermath of the August 23 Manila hostage crises have found evidence that 20 rounds were fired into the Hong Thai Tours bus by police.

Eight Hong Kong residents died during the hostage taking by Rolando Mendoza, a 55-year-old ex-cop dismissed for corruption.

The information concerning evidence of police bullets came out despite a gag order surrounding the inquiry.

Documents obtained by Filipino broadcaster ABS-CBN News disclose that police bullets hit the vehicle's windshield, driver's side window, tyres and a window near the door well.

Bullet holes linked to the line of fire of the SWAT team were also found in windows near to where some of the passengers were seated, according to the report.

Filipino authorities expect to wrap up the gathering of evidence next week.

Hong Kong Police are working in tandem with Filipino investigators who may also fly to Hong Kong to take statements from two survivors, to assist in mounting a re-enactment of the tragedy next Monday, said Filipino Justice Secretary Leila de Lima.?

Without naming the two hostages, she added the trip may be cancelled if statements taken by Hong Kong police are provided and there are no conflicts.

Following the probe, a high-level delegation will take the investigations' findings to Beijing and then to Hong Kong.

Meanwhile, two Hong Kong police officers conducting investigations in Manila were questioned briefly by Filipino authorities Thursday.

Interpol Division Chief Inspector Li Kwai-wah was denied clearance to board a flight from Ninoy Aquino International Airport to Hong Kong Thursday morning. He was stopped because he was carrying a bag of empty shell casings from the gunman's assault rifle, Chinese Embassy in the Philippines spokesman Sun Yi said.

Li had not declared the casings nor did he have the required clearance from the Philippine National Police. Li was allowed to fly out after questioning, the spokesman said.

Public anger has been simmering over the handling and aftermath of the August 23 hostage crisis during which 22 Hong Kong residents were held hostage on a busy Manila thoroughfare.

Mendoza murdered eight of the hostages before he was killed by police at the end of a bungled two-hour-long rescue attempt.

The Filipino government says it's looking into the latest in a series of blunders. The bodies of three of those killed in the incident were sent to the wrong families in Hong Kong.

Philippines Social Welfare Secretary Corazon Soliman apologized for the mix up.

The mistakes were discovered when the victims' coffins were taken to the Kwai Chung Mortuary after being flown in from Manila, according to the Security Bureau.

The bodies were identified by family members in Manila so the mislabeling may have been done by Filipino mortuary workers, a statement read.