Five days after the massive landslide that apparently buried hundreds of people here, rescue workers are stymied by unstable slopes and lack of a suitable strategy to remove the remaining bodies.

Fewer than 35 corpses have been dug out of the rubble, and work is delayed by confusion about whether survivors may be alive beneath crushed houses and tons of dirt.

Gov. Rafael Hernandez Colon announced tonight that, if no survivors are found in the next two days, a new effort to dig up the bodies with heavy machinery will begin.

He also said that, following recommendations of U.S. Geological Survey engineers, 64 families would be evacuated from a public-housing project on the back side of the hill where the landslide occurred.

Work was halted frequently today as 23 dog teams crisscrossed the steep slope and technicians followed with electronic sensors that required absolute silence in the valley to be useful.

Several times, rescue workers thought they heard tapping and scratching below ground. Trained German shepherd and Saint Bernard dogs, digging enthusiastically, identified three sites as having living creatures beneath them.

As quickly as hopes rose, they fell again. New tests did not confirm the findings, and rescue workers, digging inch by inch with shovels and pickaxes, found no sign of life tonight.

"This is breaking my heart, but we cannot give up hope," said National Guard Col. Luis Manuel Carillo, who is directing the rescue operations.

Carillo said workers could not excavate in many parts of the slope for fear of landslides. Heavy equipment could not remove walls and houses stacked at the bottom of the ravine for fear that more debris would pile into the vacuum.

"It is very difficult," Carillo said.

At times, rescue efforts were a study in frustration and confusion.

At midday, dogs being worked by teams of National Park Service employes signaled that they had found life at the bottom of the ravine below a mound of dirt and a jumble of broken cement walls.

"They wagged their tails; they barked excitedly," said Ken Hulick, head of a park service team, as he walked up a steep pathway from the site.

The dog handlers heard "kicking on a piece of tin" from under the earth, and Hulick said, "We feel pretty confident there's a live person under there."

A French civil-security team rushed to the site with electronic sensors. "Everybody stop working!" a civil-defense worker shouted into a bullhorn, as hundreds of rescue workers froze in their tracks. "Whoever is trapped in there, please give two raps on some solid object."

The tension was palpable as technician Jean Michel Blondy knelt and placed his equipment on the ground. He listened and nodded. "One can hear rapping and scratching," he said. "But it's hard to know. It could be the wind."

A dozen guardsmen and civil-defense workers frantically began dislodging a large cement slab and digging into the mud.

Suddenly, Juan Ortiz, a hefty villager with a straw hat reading "Mameyes," the name of the community that had collapsed in the landslide, ran up and shouted at the workers to stop.

"There are eight people in there," Ortiz yelled. "If you dig that way, you'll kill them all if they're still alive." He told the workers to approach the site from another angle.

The digging was stopped. For half an hour, the workers and Ortiz argued about where excavation should begin. Finally, they followed his advice.

"These disasters are very emotional things," said Richard Lewis, an Army Corps of Engineers geophysicist who arrived in the middle of the argument. "Everybody has their own idea of how to go about it."

Lewis, who with six colleagues had been up until 4:30 the previous morning combing the site with sensors, brought his own equipment to listen for taps the Frenchman had reported. He said he heard nothing, but the rescue workers continued to dig.

"We're going to continue digging this dirt fistful by fistful," said Secretary of State Hector Luis Acevedo, the commonwealth's second-ranking official.

Acevedo said geologists are checking other slopes around Puerto Rico, such as one outside Ponce called "Las Delicias," where a limestone and clay geological formation such as that of Mameyes might result in landslides.

Shantytowns built on steep slopes were widespread in Puerto Rico until the island's economic revival during the 1970s, he said. Now, he said, few are left.

No one could have predicted that Mameyes, over the last 40 years, was in danger, Acevedo said. "Nothing had ever happened before. It had lived through hurricanes and floods.