MANILA, Philippines - One of the 57 victims of the massacre in Maguindanao made a secret audio recording of the horrifying slaughter blamed on Mayor Andal Ampatuan Jr. of Datu Unsay town, who is detained at the National Bureau of Investigation (NBI) headquarters in Manila.

"Police told me they have recovered the recording device," said Esmael Mangudadatu, who lost his wife, two sisters and an aunt in Monday's attack in the Maguindanao town named after the powerful Ampatuan clan, a close ally of President Gloria Macapagal-Arroyo.

Mangudadatu said he had asked one of his sisters to hide the tape recorder in her sock when his wife and female relatives were about to leave for a local election office, accompanied by at least 30 journalists, to file his certificate of candidacy for provincial governor in next year's election.

"I asked her to turn it on as soon as they left," Mangudadatu, vice mayor of Buluan town, told dzMM radio. "It has a capacity of 288 hours or 12 days."

He said he did not join the convoy because of threats to his life.

There was no independent confirmation of the existence of the recording.

Police investigators have said they cannot reveal the details of some of the evidence they have collected.

Acting Justice Secretary Agnes Devanadera on Friday said it was possible the women were all raped before they were killed. Police said the recovered cadavers included those of 22 women.

Mangudadatu's rival for the post, Ampatuan Jr., and more than 100 armed followers stopped the six-vehicle convoy before shooting everyone dead, according to indictments released by the Department of Justice (DoJ) on Friday that charged Ampatuan with murder.

Police later recovered 57 bodies, many of them buried in mass graves beneath a mechanical digger with the name of the suspect's father, Maguindanao Gov. Andal Ampatuan Sr., printed on its side.

DoJ handling evidence

Among the dead were 30 media people.

Asked about the audio recording, Interior Secretary Ronaldo Puno told the Inquirer in a text message that evidence was being handled by the secretary of justice and did not elaborate.

In a separate text message Sunday night, Chief Supt. Raul Castaneda, of the Philippine National Police (PNP) Criminal Investigation and Detection Group (CIDG), said the Mangudadatus had not turned over any audio recording of the attack.

"They went to the NBI or DoJ," he told the Inquirer.

Sources in the DoJ and National Bureau of Investigation said they had yet to receive the audio tape referred to by Mangudadatu.

"We have yet to receive that kind of evidence," a DoJ source said in a telephone interview.

Prosecutor Edilberto Jamora of General Santos City indicated it was too early to reveal the evidence gathered so far. He also said that this information was still "off limits" to reporters.

11 witnesses

In a separate phone interview, CIDG head investigator Senior Supt. Ericson Velasquez said his office was expecting 11 witnesses to arrive from Maguindanao on Monday.

When asked if they were all policemen, Velasquez replied: "Not necessarily ... but these witnesses can shed light on what took place before the massacre."

The witnesses will be escorted by policemen to ensure their safety, he added.

Earlier, military and police authorities completed the accounting and the documentation of 429 high-powered rifles issued to four deactivated special companies of armed civilians in Maguindanao.

PNP Director General Jesus Verzosa has suspended all gun-carrying privileges issued to civilians in Maguindanao, Sultan Kudarat and Cotabato City.

The Civil Security Group (CSG) has revoked all gun licenses issued to Ampatuan Jr. on orders of Verzosa, Chief Supt. Ireno Bacolod told the Inquirer over the phone Sunday.

Records from the PNP Firearms and Explosives Division showed that Ampatuan owned four .45 cal. pistols, two 9 mm pistols, three .40 cal. pistols, two .380 cal. guns, a .357 and 5.77 mm handguns, four shotguns and two high-powered rifles.

Under the standard operating procedure, these firearms are now subject to forfeiture, Bacolod said.