A Texas researcher has admitted leaking results of a confidential research to the makers of the diabetes drug Avandia weeks before it was actually published, the journal Nature reported on Wednesday.

Steven Haffer of the University of Texas Health Science Center at San Antonio said he sent the results to GlaxoSmithKline days before the report was due to go public, which made a member of the U.S. Congress to quickly launch an investigation.

“Why I sent it is a mystery. I don’t really understand it. I wasn’t feeling well. It was bad judgment,” Haffer is quoted by Nature as saying.

The reports was released to be public on May, 21 last year in the New England Journal of Medicine and stated some pretty bad results for Avandia, namely the drug raised the risk of a heart attack by 43 percent. The results led the Food and Drug Administration to issue a safety alert, which caused Glaxo’s stock to drop. The study was led by Cleveland Clinic cardiology chief Dr. Steven Nissen, who did not give Glaxo an advance copy of the study.

Seventeen days before the article was published, Haffer faxed a copy to a GlaxoSmithKline employee he knew from working on an earlier clinical trial of the drug, Glaxo confirmed yesterday, after Nature and Republican Sen. Charles Grassley of Iowa made the matter public. In a letter released Wednesday by Sen. Grassley, he said he would like to know what Glaxo did after learning that the negative study was imminent.

“We did not contact the New England Journal,” Glaxo spokesperson Nancy Pekarek said in a telephone interview, Reuters reports.

Sen. Grassley, citing FDA documents, said Glaxo has paid Dr. Haffner about $75,000 in consulting fees and speaking honorariums since 1999.

Under The New England Journal’s rules, reviewers are prohibited from disclosing an article’s contents before publication, as a way of protecting the exclusivity of the journal’s material and protecting the intellectual property of scientists who submit articles.

“We consider the peer-review process to be confidential. Any breach of ethics by a reviewer would be taken very seriously by the editors, but would be handled as a private matter,” said a statement from the journal send by spokesperson Karen Pederson.

Dr. William Henrich, dean of The University of Texas Health Science Center at San Antonio said it was probing Haffner’s case.

“This issue has just come to light on our campus. We are embarking on a complete investigation of the facts. Once the facts are understood, we will take swift and appropriate action. The University of Texas Health Science Center at San Antonio adheres to strict ethical standards,” he said quoted by the Associated Press.