LYNN – A Lynn firefighter who collapsed while battling a 29 Oakwood Ave. house fire last week is recovering as the city’s arson squad proceeds with its investigation.Marc Duchar-me, 52, was hospitalized after he suffered medical trauma at the scene of the blaze.Although it was first beli-eved Duchar-me was stricken with a heart attack, a later analysis seemed to suggest the possibility of a blocked artery. However, investigators are waiting the results of toxicology tests that could reveal whether Ducharme inhaled harmful vapors while conducting a search for victims.Fire Lt. David Legere, head of the arson squad, said there were 1,500 to 2,000 compact discs in the basement of the burning home, which give off toxic fumes. “We don’t know what he may have inhaled at this point. We’re waiting for the toxicology tests to come back,” he said, noting that the arson probe is continuing.Legere said the fire originated simultaneously in several locations in the home, suggesting arson.Ducharme, a Lynn firefighter for the past 23 years, has been recuperating at Union Hospital.