The journal accuses Merck of withholding information on "cardiovascular outcomes" prior to submitting its manuscript of the so-called Vigor trial.

During the 2000 trial, the safety of Vioxx was compared with the popular treatment naproxen for rheumatoid arthritis.

"The evidence has raised questions about the integrity of the data on adverse cardiovascular events in the article and about some of the article's conclusions," the Journal says in a statement on its Web site.

The Journal discovered the alleged deletions as it was preparing for the deposition of it's executive editor in connection with Vioxx-related litigation.

Vioxx was withdrawn in September 2004, after it was found to double the risk of heart attack and stroke in patients.