PROVO — Brigham Young University placed physics professor Steven Jones on paid leave Thursday while it reviews his involvement in the so-called "9/11 truth movement" that accuses unnamed government agencies of orchestrating the Sept. 11, 2001, attacks on the World Trade Center.

BYU will conduct an official review of Jones' actions before determining a course of action, university spokeswoman Carri Jenkins said. Such a review is rare for a professor with "continuing status" at BYU, where Jones has taught since 1985.

Jones was teaching two classes this semester, which began Tuesday. Other professors will cover those classes, and Jones will be allowed to continue to do research in his area of academic study, Jenkins said.

Jones became a celebrity among 9/11 conspiracy-theory groups after he wrote a paper titled "Why Indeed Did the World Trade Center Buildings Collapse?" The paper was published two weeks ago in the book "9/11 and American Empire: Intellectuals Speak Out" and lays out Jones' hypothesis that the three towers fell because of pre-positioned demolition charges — not because of the planes that hit two of the towers.

When Jones began to share his demolition theory publicly last fall, he politely declined to speculate about who set the charges other than to say terrorist groups couldn't have been the source.

Then, later, he started to speak publicly about research conducted at BYU on materials from ground zero. He said he found evidence of thermite — a compound used in military detonations — in the materials.

In recent weeks, after becoming the co-chairman of the group Scholars for 9/11 Truth, Jones seemed willing to go further, implicating unnamed government groups but not President Bush.

The Deseret Morning News requested a statement from the university Wednesday afternoon for a story it was preparing on Jones and his high-profile role in the 9/11 truth movement. University officials informed Jones of the decision to place him on leave Thursday afternoon and released a statement to the newspaper Thursday night.

"BYU has repeatedly said that it does not endorse assertions made by individual faculty," the statement said. "We are, however, concerned about the increasingly speculative and accusatory nature of these statements by Dr. Jones."

Last fall, BYU faculty posted statements on the university Web site that questioned whether Jones subjected the paper to rigorous academic peer review before he posted it at physics.byu.edu. Jones removed the paper from BYU's Web site Thursday at the university's request.