By Bob Tourtellotte

LOS ANGELES (Reuters) - Federal officials may be planning to subpoena filmmaker Michael Moore seeking information about a trip he took to Cuba for his documentary, "Sicko," a source close to the situation said on Friday.

In a late Thursday appearance on NBC's "The Tonight Show with Jay Leno," Moore said he was notified at the TV studio in Burbank, California, that a subpoena had already been issued.

But the source, who declined to be identified, said Moore had not actually been served with the request. Rather, the office of his attorney, David Boies, was contacted by a division of the U.S. Department of Commerce seeking the name of a person who would accept a subpoena on Moore's behalf.

"Sicko" takes a scathing look at the U.S. health-care system through the eyes of people who suffered injuries or had diseases and felt the U.S. system of insurers and drug providers failed them.

The director took several Americans, who became ill after working in the ruins of New York's World Trade Center following the Sept. 11 attacks, for free treatment in Cuba.

In May, the U.S. Treasury Department informed Moore it was investigating his trip to the communist state as a potential violation of Washington's long-standing embargo restricting U.S. citizens' travel to the communist nation.

Moore wrote then to U.S. Treasury Secretary Henry Paulson, "I have broken no laws, and I have nothing to hide."

A representative for Moore referred calls to Boies, who was not immediately available to comment.

"Sicko" has received mostly good reviews from film critics, but some viewers have criticized it for a lack of a substantive comparison of the U.S. health-care system with countries like Cuba that offer universal health care.

The Weinstein Company, the studio behind "Sicko," declined to comment on a possible subpoena.

Weinstein Co. plans to donate 11 percent of the movie's box office on Aug. 11 to a fund to help rescue workers suffering from ailments relating to their work at Ground Zero.

Moore won an Academy Award for 2002's anti-gun documentary "Bowling for Columbine." He took a critical look at President George W. Bush's war against terrorism in his 2004 documentary "Fahrenheit 9/11."

(additional reporting by Stephanie Bagley)