Three Harvard Medical School specialists who recently investigated Philadelphia's mysterious Legionnaires' disease say they think either toxic compounds or an unknown infectious agent caused the disease.

The three specialists, Dr. Morton N. Swartz, professor of Medicine; Dr. Louis Weinstein, visiting professor of Medicine, and Dr. Alexander D. Langmuir '31, visiting professor of Epidemiology, were part of a panel of seven invited by the Center for Disease Control in Atlanta to review data on the Legionnaires' disease there.

The panel came up with no conclusive findings, but recommended further investigation of toxic compounds and studied possible epidemiological causes of the disease, Swartz said yesterday.

"There was no evidence of the usual infectious agents such as bacteria, fungus, or the common respiratory viruses," he added. Swartz also said that there have been no secondary outbreaks that would indicate the disease is infectious.

Langmuir said the panel left Atlanta two weeks ago with no "coherent" theory about the cause or spread of the disease. "To be this much in the dark when you have a lifetime of experience is rather embarrassing," he added.

The cause of the disease may never be found, Swartz said. Both he and Langmuir agree, however, that it is unlikely the disease will break out again.

Paul Horowitz, '65, professor of Physics, together with a group of other physicists, two weeks ago ended a three month examination of the hair of disease victims to detect evidence of metal poisoning.

Horowitz compared the Legionnaires' hair to the hair of victims of lead, mercury, and arsenic poisoning. He concluded the victims were poisoned by none of these substances.

He also scanned the hair for all elements heavier than magnesium, but found no consistent patterns that could explain the Legionnaires' poisoning.

The examination of the Legionnaires' hair is particularly helpful, Horowitz explained, because hair retains toxin much longer than the rest of the body.