MANILA - Six bodies have been unearthed from the "killing fields" in Ampatuan, Maguindanao province on Wednesday, bringing the death toll of the bloodiest election-related incident to 52.

A report by ABS-CBN Cotabato said four bodies -- three men and a woman -- were initially retrieved from a UNTV van and a red Toyota Vios with an official seal of the Tacurong City local government.

The two vehicles were part of a six-vehicle convoy of the Genalyn Tiamzon-Mangudadatu, who was supposed to file a certificate of candidate for governor on behalf of her husband, Buluan Vice-Mayor Ismael Mangudadatu.

At past noon, two more bodies were also recovered from the site. Retrieval teams were also trying to dig out a blue Toyota Tamaraw FX, which was initially reported as being driven by a son of a local official in Maguindanao.

Media people were also part of the convoy, including the UNTV van. They were supposed to cover the filing of the COC in Sharif Aguak town.

Police said a group of at least 100 gunmen ambushed the convoy and ordered members of the Mangudadatu family and the media men out of their vehicles before shooting them all dead. There were indications that the women were raped.

An initial list of media people included in the convoy, as gathered by ABS-CBN, showed 4 members of a UNTV network crew. They were identified as Joy Duhay, Victor Nuñez, Macmac Ariola and Jimmy Cabillo.

The National Union of Journalists in the Philippines said a total of 12 journalists have been recovered from the burial site as of Monday night. The NUJP said they expect the number to increase to 20.

ANC's executive producer Patricia Evangelista, who was at the retrieval site, reported that authorities were expecting the death toll to increase to more than 60.

Evangelista said there were reports that people on board vehicles that were not part of the Mangudadatus' convoy were also stopped and shot dead.

The military said the main suspects in the abductions and murders were gunmen hired by the Maguindanao governor, Andal Ampatuan, and his son who has the same name.

Relatives of the victims and witnesses have said the powerful political clan wanted to stop Mangudadatu from challenging Ampatuan junior for the post of governor in next year's national elections.

Three policemen believed loyal to the Ampatuans have been detained for their alleged involvement in the murders.

Following the massacre, President Gloria Arroyo imposed emergency rule on Maguindanao, neighboring Cotabato City and nearby Sultan Kudarat province. -- Reports from Lerio Bompat, ABS-CBN Cotabato, Patricia Evangelista, ANC executive producer and Agence France-Presse