PORTLAND, Ore. – Former Vice President Al Gore was cleared Friday of allegations he groped and assaulted a masseuse in a luxury Portland hotel room in 2006, closing a case that could have tarnished the Nobel prize winner’s reputation.

After a four-week investigation that included interviews with Gore, masseuse Molly Hagerty, her acquaintances and hotel staff, as well as testing a pair of stained pants belonging to Hagerty, Multnomah County District Attorney Michael Schrunk said Friday there was no basis for prosecution.

In a memo to Schrunk released with the decision, Senior Deputy District Attorney Don Rees cited “contradictory evidence, conflicting witness statements, credibility issues, lack of forensic evidence and denials by Mr. Gore.”

Rees also said Hagerty and her attorneys were uncooperative, witnesses could not remember anything unusual, Hagerty failed a polygraph exam, and she would not say whether she was paid by a tabloid newspaper for her story.

Gore aides welcomed the news.

“Mr. Gore unequivocally and emphatically denied this accusation when he first learned of its existence three years ago,” spokeswoman Kalee Kreider said.

“He respects and appreciates the thorough and professional work of the Portland authorities and is pleased that this matter has now been resolved.”

Gore and his attorneys met July 22 with Portland detectives in San Francisco, telling them he remembered almost nothing about the woman and was “completely baffled” by her statements, according to the memo.

Among the contradictory or conflicting statements about the alleged incident at the Hotel Lucia in downtown Portland on Oct. 24, 2006, prosecutors noted:

• Hagerty, who has red hair, said she called Gore after the alleged incident to tell him to “dream of redheaded women, seemingly in contradiction to her assertions she was terrified of Mr. Gore.”

• Forensic testing by the Oregon State Police crime lab of a stain on pants that Hagerty said she was wearing during the encounter with Gore was negative for any seminal fluid.

• An attorney for Hagerty told detectives she had taken a polygraph exam about her allegations and failed.

• Two days after the encounter, Hagerty sent an e-mail to Hotel Lucia thanking managers for the referral and saying she was more than confident that Gore “was completely happy with the professional services I delivered.”

It does not mention any problems.