The release of two books by author and motivational speaker James Arthur Ray has been postponed in the wake of three deaths that occurred after a sweat lodge ceremony he led this month in northern Arizona.

Hyperion Books publicity director Marie Coolman said Tuesday that the December release of a paperback version of Ray's best-selling book "Harmonic Wealth" and a new hardcover title, "The Seven Laws of True Wealth," will be delayed until late winter.

She had no comment on what led to the decision.

The delay comes as authorities continue a criminal investigation into the Oct. 8 sweat lodge ceremony at a high-priced retreat outside Sedona, Ariz., that left three dead and nearly 20 others hospitalized.

Lawyers for several of the victims have said they plan to pursue lawsuits, although none have been filed.

Calls to Ray's spokesman, Howard Bragman, were not returned Tuesday.

Also Tuesday, U.S. Sen. Amy Klobuchar, D-Minn., asked the Department of Justice and the Federal Trade Commission to investigate Ray's Spiritual Warrior program. One of the victims was from Minnesota.

"People came from all parts of the country to attend an event which they believed would enhance their lives," Klobuchar said in a statement. "Instead, three people died, 18 were hospitalized and dozens more were traumatized. Mr. Ray neither enhanced their lives nor protected their safety."

Klobuchar asked the FTC to review Ray's marketing and advertising practices and also asked Attorneying the deaths as homicides but have yet to determine the cause. Ray has hired his own investigative team to try to determine what went wrong and vowed to continue holding seminars despite criticism.

"I have taken heat for that decision, but if I choose to lock myself in my home, I am sure I would be criticized for hiding and not practicing what I preach," he wrote on his blog last week.

Ray has become a self-help superstar by packaging his charismatic personality and selling wealth. He uses free seminars to recruit people to expensive seminars like the Sedona retreat that led to the sweat lodge tragedy.

He also markets his own line of self-help books, often pushing them to participants at his events.

Beverley Bunn, a 43-year-old Texas resident who participated in the sweat lodge ceremony, said Ray touted his new book at his retreat and asked everyone to buy multiple copies for family and friends so he could make the New York Times' best-seller list.