About 2,500 police officers were deployed as participants, who included soldiers, religious leaders, politicians and movie stars, raced across the capital to raise funds to clean up one of 48 tributaries flowing into the Pasig River, officials said.

Metropolitan Manila police chief Leocadio Santiago said about 175,000 people joined, although the organizer, a foundation of the ABS-CBN TV network, estimated slightly over 100,000 may have finished the race in four distances that ranged from 2 to 13 miles (3 to 21 kilometers).

Organizers also said they wanted to break a Guinness World Record for the most number of people joining a foot race. A Manila auditing firm would verify the actual number of participants, they said.

The 15.5 mile-river, which flows across a number of towns and cities and along the Malacanang presidential palace, has long been believed to be biologically dead because of pollution blamed on refuse from shantytowns and toxic waste from industrial plants.

In August, new President Benigno Aquino III inspected a stretch of the river that teemed with shanties and garbage and promised to take steps to have it cleaned in his six-year term.

Aside from serving as a key transport route, the foul-smelling river — often choked with water lilies and trash — has been at the forefront of recent history.

Rebel troops planned to use the river to launch a coup against then dictator Ferdinand Marcos in 1986 but were found out. A crackdown against the rebels then sparked the 1986 nonviolent "people power" revolt that ousted Marcos.

Waving goodbye to his supporters, popular President Joseph Estrada rode a ferry across the river in a poignant scene as he left the presidential palace in 2001 after being ousted by another "people power" revolt over alleged corruption and misrule.