Nearby, bodies were being laid out under banana leaves Tuesday as police _ their faces covered against the stench _ unearthed a mass grave containing 22 victims from Monday's ambush on an election caravan. The discovery brought the death toll to 46 _ an unprecedented act of violence at the outset of the country's election season.

As many as five people remained unaccounted for.

President Gloria Macapagal Arroyo declared a state of emergency in Maguindanao and a neighboring southern province, sending extra troops and police to try to impose the rule of law.

"No effort will be spared to bring justice to the victims and hold the perpetrators accountable to the full limit of the law," she said.

Few think she will be successful in the impoverished, lawless region that has been outside the central government's reach for generations, and where warlords backed by private armies go by their own rules.

Authorities said the victims included at least 13 Filipino journalists from regional newspapers, TV and radio stations who were accompanying family members and supporters of a gubernatorial candidate out to file his nomination papers for May 2010 elections.

Noynoy Espina, vice chairman of the National Union of Journalists of the Philippines, said as many as 20 journalists may have been in the convoy, based on reports from union chapters in the area.

The figures could not be immediately reconciled, but still the deaths marked "the largest single massacre of journalists ever," according to Paris-based Reporters Without Borders.

Dozens of gunmen intercepted the caravan as it traveled on a two-lane highway that cuts across vast open tracts of land and banana groves, police said. They took some of the people to the grassy area, where the killings started.

Authorities found 24 bullet-riddled bodies sprawled on the ground next to five abandoned vehicles.

Police, aided by a backhoe, worked most of Tuesday to extricate the bodies from the mass grave. All had been shot multiple times and were dumped on top of one another. One was a pregnant woman.

Grieving relatives helped identify their loved ones before they were given the bodies, covered by banana leaves, for burial.

The gubernatorial candidate, Ismael Mangudadatu, was not in the convoy because he had received death threats. He accused a powerful political rival from the Amputuan clan of carrying out the killings.

Mangudadatu's wife, Genalyn, and his two sisters, were among the dead, he said. In all, 21 women and 25 men died, said military spokesman Col. Jonathan Ponce.

Mangudadatu said four witnesses in his protection, whom he refused to identify, had told him the convoy was stopped by gunmen loyal to Andal Ampatuan Jr., a town mayor and rival, to prevent Mangudadatu's family from filing election papers.

"It was really planned because they had already dug a huge hole (for the bodies)," Mangudadatu said.

He said there were reports from the area that the militia had been blocking the road for a few days.

The Ampatuans, who have ruled one of the nation's poorest regions since 2001, could not be reached for comment.

Arroyo's peace adviser Jesus Dureza said he met Tuesday with Andal Ampatuan, the family's patriarch, and received assurances that his family would cooperate in the investigation.

It was not clear how far Arroyo's administration would go in trying to force the provincial warlords to give up their weapons and private armies.

But Maguindanao's provincial police chief and three other officers were relieved of duty and confined to camp after they were reported to have been seen with the pro-government militiamen who stopped the convoy, police said.

Such militiamen are meant to act as an auxiliary force mobilized by the police or military to fight rebels and criminals, but often they act as private enforcers of local warlords.

Much of the southern island of Mindanao, including Maguindanao province, used to be ruled by fiercely independent sultans who fought Spanish and American colonizers. The political dynasties of the Ampatuans and the Mangudadatus behave in a much similar way _ ruling by force, unopposed in their turfs with little outside interference.

Julkipli Wadi, a professor of Islamic studies at the University of the Philippines, said he doubted the national government's resolve in trimming the powers of political dynasties like the Ampatuans because they deliver votes during elections.

"Because of the absence of viable political institutions, powerful men are taking over," he said. "Big political forces and personalities in the national government are sustaining the warlords, especially during election time, because they rely on big families for their votes."