Perched tensely in a niche in the ruins of the Juarez Hospital, the French Navy firemen called out for the third time for quiet.

"Silencio!" one of the jumpsuited rescue technicians ordered in thickly accented Spanish.

The crowd of rescue workers, reporters and visiting diplomats stood hushed below as the Frenchmen trained their ultrasound detector deep into the shattered building's interior. Dade County (Fla.) Fire Department Lt. Douglas Jewett paced impatiently, anxious to resume the excavation of the tunnel he hoped would free the man and two women known to be still trapped alive this afternoon, more than a week after last Thursday's earthquake leveled the 14-story hospital tower.

"We hear a noise," one of the Frenchmen hissed. "We can hear someone scratching."

The crowd sighed, and the hubbub of the often chaotic rescue effort slowly resumed.

"Play ball!" Jewett shouted. "People are dying!"

Clashing frequently with their Mexican and American colleagues and proud to the point of arrogance of being on the cutting edge of rescue technology, the specialized 45-man team of French Navy firefighters have emerged as heroes of the multinational rescue effort.

Working here since Saturday with their orbiphone, an ultrasound detector that they said could detect the sound of pen on paper through 120 feet of rock, the French Navy squad has been able to do something no one else here has done. They have pinpointed the locations of earthquake survivors entombed beneath tons of rubble in places where most rescue officials at first thought they would be impossible to find.

"Those guys are real professionals," said Dade County Fire Department Lt. James Arias, a bilingual coordinator of the rescue effort.

Here at the Juarez Hospital, rescue workers at 7:40 this morning pulled from deep within the building a weak but apparently healthy 8-day-old baby in a metal crib, the eighth earthquake survivor to be rescued there in a 14-hour period.

After extracting one infant survivor at dusk yesterday, rescue workers pulled out three more babies two hours later, a woman patient shortly after midnight, and another infant at 3:30 a.m., followed shortly by a nurse, reported Arias and Commander Alfonso Esquer of the Mexicali Fire Department.

Whisked into incubators and off to an Army hospital, the rescued infants began eating normally today and seemed to have suffered no permanent injury, reported Lt. Col. Rolando Cuevas Uribe, head of pediatrics at the Military Hospital.

"They are durable, made in Mexico," Cuevas said, grinning. "This is the biggest miracle since the 1969 Mets."

The adult survivors also emerged physically healthy, but appeared to have been severely traumatized by their ordeal, rescue workers said.

"They appeared pretty shaken up, but they had been enclosed in tiny spaces next to corpses for a week without food or water or light," Arias noted.

Encouraged by their success, the rescue workers at Juarez Hospital have redoubled their efforts. "We are working against the clock," said Esquer. "Today is really the key day."

Adults can survive up to 10 days without food or water, but after that "their chances of survival begin dropping drastically," said Serge Plagnol of the French Navy team.

The French and other foreign volunteers said they feel pressure from the Mexican government to end the search and yield to the demolition and fumigation teams assigned to clear away the rubble. Demolition would end the hopes of survival for anyone left alive in the wreckage. Most of the volunteers conceded that with the risk of epidemics increasing the painful decision to call a halt to the rescue efforts must be made soon. "I hope that it won't be for a few days more, but someone is going to have set a deadline sometime," Arias said. "I wouldn't want to be that someone."

Elsewhere in the devastated city center, that decision has quietly been made. At the Benito Juarez public housing complex this morning, bulldozers and cranes followed by men carrying tanks of disinfectant on their backs pushed through the wreckage of what had been a 380-unit apartment building. Health authorities had worried that the decaying corpses would contaminate ground water running beneath the complex.