BETHESDA, MD — A special colony of 130 mice that had been genetically altered to develop AIDS was destroyed by a worker at the National Institutes of Health who mistakenly cut off all air to the sealed chambers they lived in.

The mice, whose cells each contained a copy of the AIDS virus' genes, were the first completely successful animal models of the fatal disease. The experiment has been viewed by AIDS experts as one of the most promising and important in the country.

The mice carried the AIDS genes in every cell in their bodies and were the first animals other than humans to become sick.

Its abrupt interruption is expected to slow the rapid pace at which scientists are discovering how the AIDS virus works.

"I look at this as a pretty major setback for my program and for AIDS research at NIH," said Malcolm Martin, a leading virologist at the National Institute of Allergy and Infectious Diseases, who had directed the research at the Bethesda, Md., laboratory. "We had a great disease model. And now we will have to repeat most of our work. Obviously, it's somewhat distressing."

Martin said it will take at least five months to breed enough mice to continue the research at its recent pace.

The mouse experiments began more than a year ago when, under some of the tightest security ever imposed on NIH research, scientists started raising mice carrying genes for the AIDS virus in every cell in their bodies. The genes, copies of those carried by the AIDS virus, were spliced into the chromosomes of the mice in early embryonic stages.

The controversial experiment had major implications. It was the first in which the complete genetic code for an organism causing a fatal human disease had been inserted into another animal species, and the mice were the first animals other than humans to become sick as a result of the human immunodeficiency virus, which causes AIDS.

The mishap occurred Saturday when the building was undergoing regular preventive maintenance and electrical power was cut to replace a control device that helped regulate the heating, air conditioning and alarm systems, according to NIH officials.

"I don't think we have much choice but to laugh and start over."

When the maintenance was completed, the worker who installed the new device apparently believed he had restored power to the entire building and left. When researchers came in early Sunday morning they found the laboratory without power and only three of the 130 mice alive.

The project's initial results, showing that the mice developed symptoms almost identical to those commonly found among infants with AIDS, were presented earlier this year at the Fourth International Conference on AIDS in Stockholm.

"I lay in bed for a long time just after they called me," Martin said yesterday. "But what can you really do? I don't think we have much choice but to laugh and start over."