Workers renovating McKinley High School in Northeast Washington this week ripped up and apparently disturbed old insulation containing high levels of asbestos, which is known to cause cancer.

Workers at the site said their activity has kicked up substantial amounts of dust from the asbestos-laden material. A coating of dust was visible in the top-floor work site yesterday, as were dusty footprints that workers left in other parts of the building. Asbestos is dangerous in the form of airborne particles.

Shelton Lee, director of safety and security for the District schools, said air samples taken Thursday and yesterday indicated no danger to the more than 1,000 students at the school or the workers who handled the asbestos material.

"We found a high level of asbestos in the samples taken from the floor but an infinitesimal low level from the air sample," he said. "The danger is from what is in the air."

However, he said he had ordered the contractor on the job to partition off the third floor, where the asbestos was found, with plastic sheeting by Tuesday, when classes resume at the school. No attempt had been made by yesterday to seal off the area containing the asbestos.

Frederick Douglas, a lawyer whose firm has been hired by the school board to help in responding to a court-ordered asbestos abatement program in the schools, called the situation at McKinley "an emergency."

"I'm shocked that work would continue on a work site where there was even a hint of asbestos," he said. "If the school system had been notified, they would have acted immediately by sending in the asbestos abatement team. We don't let people go about getting exposed to asbestos."

Tests on the material showed it was 55 percent asbestos, according to Tara Hamilton, spokewoman for the Department of Public Works, which selected the Sherman R. Smoot Co. to do the McKinley renovation.

About 20 workers were at the McKinley job site yesterday. None was seen wearing a mask or other protection against the asbestos, which was discovered as workers dug into the floor to lay new electric lines.

Persons working around asbestos often are required to wear protective devices, and additional safety steps are generally taken.

"The guys told me that stuff was asbestos, but I am safe as long as I don't handle it," said James Robins, 26, who has been building scaffolding at McKinley, located at Second and T streets NE.

"No one has told us to wear face masks, so it must be okay to work here," Robins said.

Elsie Sharon, technical supervisor of industrial hygiene at American Medical Laboratories, a private testing lab in Fairfax that examined the asbestos material at the request of The Washington Post, said the asbestos found at McKinley presented a potential health hazard.

"When working with even low levels of asbestos, workers have to take certain precautions, including the wearing of respirators, misting the area to keep the dust down and controlling the air flow in the building," she said.

Sharon added that "the airborne particles are so small that they can't be seen," a fact that magnifies the potential health hazard.

Asbestos insulation was popular in construction work from the 1940s until 1972, when it was banned because of its cancer-caus ing properties. Asbestos dries out over time and can separate into tiny airborne fibers that settle in lungs and can cause cancer or severe scarring of lung tissue.

According to Sharon, material containing as much asbestos as that found at McKinley must be removed under strict safety regulations.

City spokeswoman Hamilton said that on Tuesday a firm hired by the contractor will chemically spray the exposed asbestos insulation and then seal it off.