A state of emergency was declared in nine provincial areas near Manila, setting government relief efforts in motion. And for much of the day Tuesday, the only major highway linking Manila to the north of the country was flooded and closed to traffic.

The flooding is the worst to hit the area since two storms in 2009 killed more than 900 people.

On Monday, the government said up to half of the city and its environs were under water. On Tuesday, officials said some of the storm waters had receded, but heavy rains continued, leaving open the possibility that floods would again claim more of the city.

Schools and business and government offices were ordered closed, although Manila’s main business districts were largely spared, in part because they have well-maintained drainage systems, unlike slum areas.

Richard J. Gordon, chairman of the Red Cross of the Philippines, described a perilous situation for rescuers, many of whom were using rafts and makeshift boats to traverse flooded slums.

“We have areas where our people can’t get in because there are live wires in the water,” Mr. Gordon said. “They face the risk of electrocution.”

He added, “We just have to grin and bear it and do our best to rescue people.”

In Quezon City, just northeast of Manila, nine people, including three children, were killed Tuesday when a landslide caused by heavy rain buried a slum.

As rescuers frantically tried to dig people out, Jessie Bailon stared at a muddy mound where his shanty had stood. “My wife, children and grandchild are down there,” he said, according to The Associated Press.