NEW YORK – A Senate report said Saturday that drug maker GlaxoSmithKline knew of possible heart attack risks tied to Avandia, its diabetes medication, years before such evidence became public.

Sen. Max Baucus, chairman of the Senate Finance Committee, and Chuck Grassley, the committee’s ranking Republican, released the report, which follows a two-year inquiry. They are also asking the U.S. Food and Drug Administration why it allowed a clinical trial of Avandia to continue even after the agency estimated that the drug caused 83,000 heart attacks between 1999 and 2007.

The agency ordered a warning to be included on Avandia’s label in 2007, saying that it might increase the risk of heart attacks, although the data on those risks was inconclusive. Soon afterward Grassley, one of the FDA’s toughest critics in Congress, disclosed that the agency’s internal safety experts came within one vote of recommending a withdrawal of Avandia.

In a letter to FDA Commissioner Margaret Hamburg, the senators said the committee’s report was based on researchers’ studies of Avandia, internal GlaxoSmithKline documents and FDA documents. They said investigators interviewed GlaxoSmithKline and agency employees as well as what it called anonymous whistleblowers.

Based on its knowledge of the heart attack risks, GlaxoSmithKline ”had a duty to sufficiently warn patients and the FDA of its concerns in a timely manner,” the report said.

Instead, the company tried to downplay findings that the drug could increase cardiovascular risks while also working to downplay findings that a rival medication might reduce such risks, it said.

GlaxoSmithKline said in a statement the drug is safe. It said the committee report took data out of context from analyses of Avandia.

In May 2007, the New England Journal of Medicine published an analysis of dozens of studies on nearly 28,000 people who had taken Avandia. The journal said there was a 43 percent higher risk of heart attack for those taking Avandia compared to people taking other diabetes drugs or no diabetes medication. The findings raised concerns because two-thirds of the people with Type 2 diabetes, the most common form, die of heart problems.