Two Food and Drug Administration researchers were burned yesterday when the liquid in a beaker they were using in a laboratory experiment suddenly exploded, spewing acid and broken glass on them, FDA officials reported yesterday.

"I didn't know what had happened," said Federal Protective Service Officer R. A. Tibbs, who was on duty at the building's entrance. "(This) lady came running out and screaming. Blood was steaming down her face. She just kept running. I tried to stop her, but she ran down the hall. I thought she had been shot."

Tibbs said he ran to the laboratory area, where he found another woman, soaking her face in a basin of water.

The two women, Zelma Willard and Barbara Harland, were taken to the Washington Hospital Center, where they were treated for chemical burns. Harland was later released, but Willard was admitted and is in good condition.

A hospital spokesman said Willard was being treated for minor burns on one arm and a knee.

Dorie Waddick, the acting safety manager for FDA's bureau of foods, said the two women had gone to the building at 2nd and C Streets SW yesterday to work on the experiment.

Harland, who is a research biologist, and Willard, a laboratory technician, were digesting biological samples in glass enclosure.

Waddick said she did not know why the acid solution exploded. Federal Protective Service officials said sulfuric acid in the solutin had mixed with gas fumes to cause the explosion.

Waddick said it is standard procedure for some of the FDA's researchers to do weekend work on experiments.

She said injuries to the two women were minimal because they were wearing protective glasses and coats. Waddick said there was no major damage to the laboratory.