The government’s own preliminary evaluation of the diabetes pill Avandia confirms the heart risks reported in a study earlier this week and suggests that as many as 60,000 to 100,000 heart attacks might be linked to its use since it came on the market eight years ago, a leading member of Congress said Thursday.

In a floor statement placed in the Senate record, Sen. Charles Grassley also said that safety watchdogs within the federal Food and Drug Administration “several months ago” recommended a “black box” on the drug’s label – the strongest possible warning.

It is the first confirmation that the FDA’s own analysis of Avandia shows a similar magnitude of heart attack risks – dangers that were first publicly raised in a medical journal report published earlier this week.

Grassley complained that FDA higher-ups have said they want to wait for results of an ongoing study that will not be available for two more years before making a decision.

The FDA has been under fire since Monday’s report came out, attacked by consumer advocates for dropping the ball on drug safety and for taking no stronger action in light of the new warning signs.

Avandia, sold by the British company GlaxoSmithKline PLC, is a blockbuster medication used to treat Type 2 diabetes, the most common form of the disease. More than 6 million people worldwide have taken the drug, whose U.S. sales topped $2.2 billion last year.

GlaxoSmithKline strongly disputes the conclusions.