A day after facing down a military mutiny, President Gloria Macapagal Arroyo (search) vowed Monday to punish the rebellious officers and ordered an investigation into the causes of the uprising that shook her presidency.

In a state of the nation speech, Arroyo assured Filipinos that she was still in control and said mutineers "will be met with the full force of law."

Hours earlier, police arrested a key supporter of Joseph Estrada (search), the disgraced ex-president Arroyo replaced after his ouster by popular protest in 2001.

Officials alleged that several Estrada cronies aided and fomented Sunday's rebellion that ended without bloodshed after a 19-hour standoff in downtown Manila.

Lawyers for the ex-leader, who has been in custody for more than two years as he stands trial for corruption, insisted that Estrada had nothing to do with Sunday's drama.

Arroyo, who many regard as Estrada's nemesis, did not mention any political plans, but the force of her words fueled speculation that she might reverse an earlier promise not to stand in next year's presidential election.

"I am constituting an independent commission to investigate the roots of the mutiny and the provocation that inspired it," she told the Congress.

She also announced a plan to reform the police force, branded as corrupt and inept following the July 14 escape of three terror suspects thought to have bribed their way out of its main Manila headquarters.

Arroyo, however, failed to outline a widely expected change of senior police commanders -- something that had been included in a draft of her speech supplied to reporters.

The reason for this last minute omission was not immediately clear.

However, earlier on Monday, police announced they were using emergency powers granted by Arroyo to detain some of Estrada's associates suspected in the mutiny case.

The first to be nabbed was Ramon Cardenas (search), a member of Estrada's Cabinet.

Officers said he owned a "safe house" for the rebel troops -- stacked with assault rifles, ammunition and the same red armbands used by the soldiers who seized an apartment and ritzy shopping complex in downtown Manila.

The nearly 300 mutineers demanded the resignation of Arroyo, but backed down during talks with government negotiators.

Amid heightened security fears, about 3,000 police officers and sharpshooters were deployed outside the Congress building for Arroyo's speech.

Outside, thousands of protesters called for Arroyo's resignation, citing her failure to give land to poor farmers, control graft and ease crushing poverty.

"The people's call for Arroyo's resignation will continue to escalate, especially after the mutiny by young officers and soldiers," labor leader Elmer Labog said.

Protesters danced, sang and burned a 12-foot effigy of Arroyo with moving legs, symbolizing the president on the run.

Arroyo traveled to Congress aboard a helicopter.

Hundreds of renegade soldiers were confined to barracks and junior officers who led the mutiny were under arrest and questioned ahead of likely courts martial.

Police investigated the possible involvement of Arroyo's political rivals amid fears that she is the target of a wider destabilization campaign ahead of next year's election.

Arroyo has yet to rescind her weekend declaration of a state of rebellion that gives authorities power of arrest without warrant.

The Philippines has had about eight military uprisings and coup attempts since the "people power" ouster of dictator Ferdinand Marcos in 1986.

The weekend's drama -- complete with tanks and troops -- was played out in the streets of the capital's Makati financial district. Although calm returned there Monday morning, nervous stock and currency markets slid and then partially recovered.

Five junior officers, who organized the brazen uprising, were being questioned under guard, said army spokesman Lt. Col. Joselito Kakilala.

About 300 mutinous troops who followed them in the takeover in Makati had been disarmed and were ordered to stay in their barracks.

The renegades wired the apartment and shopping complex -- home to some of the city's richest citizens, foreign businesspeople and diplomats -- with explosives and booby traps.

The renegades, who complained of corruption and misconduct in the upper ranks of the military and government, gave up without bloodshed. They also complained that Muslim and communist rebels were buying weapons and ammunition from the military.

They spent the night in the stadium of a nearby army base and were disarmed. They were later transferred to the home bases as an investigation was launched.