LOS ANGELES — Academy Award-winning filmmaker Michael Moore is under investigation by the U.S. Treasury Department for taking ailing September 11 rescue workers to Cuba for a segment in his upcoming health-care documentary “Sicko,” the Associated Press has learned.

The investigation provides another contentious lead-in for a provocative film by Mr. Moore, a fierce critic of President Bush. In the past, Mr. Moore’s adversaries have fanned publicity that helped the filmmaker create a new brand of opinionated blockbuster documentary.

“Sicko” promises to take the health-care industry to task the way Mr. Moore confronted America’s passion for guns in “Bowling for Columbine” and skewered Mr. Bush over his handling of September 11 in “Fahrenheit 9/11.”

The Treasury Department’s Office of Foreign Assets Control notified Mr. Moore in a letter dated May 2 that it was conducting a civil investigation for possible violations of the U.S. trade embargo restricting travel to Cuba. A copy of the letter was obtained Wednesday by the AP.

“This office has no record that a specific license was issued authorizing you to engage in travel-related transactions involving Cuba,” Dale Thompson, OFAC chief of general investigations and field operations, wrote in the letter to Mr. Moore. In March, Mr. Moore took about 10 ailing workers from the Ground Zero rescue effort in Manhattan for treatment in Cuba, said a person working with the filmmaker on the release of “Sicko.”

In a statement yesterday, “Sicko” producer Meghan O’Hara said the Treasury investigation might be an attempt to undermine the film.

“Our health-care system is broken and, all too often, deadly,” Ms. O’Hara said. “The efforts of the Bush administration to conduct a politically motivated investigation of Michael Moore and ‘Sicko’ will not stop us from making sure the American people see this film.”

After receiving the letter, Mr. Moore arranged to place a copy of the film in a “safe house” outside the country to protect it from government interference, said the person working on the release of the film.

September 11 rescue workers “risked their lives searching for survivors, recovering bodies, and clearing away toxic rubble,” Ms. O’Hara said. “Now, many of these heroes face serious health issues, and far too many of them are not receiving the care they need and deserve.”

Treasury officials would not comment specifically about Mr. Moore’s case. But department spokeswoman Molly Millerwise said OFAC is “required to investigate potential violations of these programs. In doing so, OFAC issues hundreds of letters each year asking for additional information when possible sanctions violations have occurred.”

The letter noted that Mr. Moore applied October 12, 2006, for permission to go to Cuba “but no determination had been made by OFAC.” Mr. Moore sought permission to travel there under a provision for full-time journalists, the letter said.

According to the letter, Mr. Moore was given 20 business days to provide OFAC with such information as the date of travel and point of departure; the reason for the Cuba trip and his itinerary there; and the names and addresses of those who accompanied him, along with their reasons for going.