A spring break trip to Cuba taken by students and a teacher from a New York City public high school has raised concerns about whether the group violated U.S. travel restrictions to the Communist country.

"We are investigating," Mayor Michael Bloomberg told reporters Monday.

A city Department of Education spokesman said this month's trip to Cuba was not officially sanctioned by the Beacon School, although the school's Web site featured a call for applications and a list of selected students, as well as details of previous sponsored trips to the island.

"We were told that it violated State Department travel restrictions," department spokesman David Cantor said.

Molly Millerwise, spokeswoman for the U.S. Treasury Department, declined to comment on the case.

The department hands out travel licenses for Cuba trips, and Millerwise said permission is granted to some groups, including for those seeking to engage in religious activity or humanitarian aid. Educational licenses also are granted, but not at the high school level, she said.

People who violate sanctions can face penalties ranging from warnings to a $65,000 fine.

Cantor said the education department had asked a special investigator to see if any school regulations were violated on this trip or previous ones. However, it's unclear what the education department could do if the teacher, Nate Turner, and the students acted independently, Cantor said.

In 2004-05, according to the school Web site, students had to take a class if they wanted to go on a trip to Cuba.

In mid-October, Turner posted a release on the school's Web site advertising that applications for this year's trip were available. An essay was one of the requirements. It was unclear how many students actually went on the trip, though a school Web site posting listed about 30 students who had been selected for it.

Turner did not respond to an e-mail request seeking comment on Monday. Neither did school principal Ruth Lacey, though she told the New York Post that the school had denied approval for the trip but that Turner went ahead and arranged it.

Lacey told the paper the previous trips to Cuba had been approved. "At the time, I think the climate in the country was different," she said.

Lee Kalcheim, whose twin sons chose not to go after being told only one could take the trip, said he felt it was ridiculous that there would be any problems with such a foray.

"Our policy toward Cuba is nonsense," Kalcheim said Monday. "You antagonize. You just make things worse. We should have just had normal relations with them."

Traveling to Cuba has been difficult for more than 40 years because of the country's rocky relations with the United States. In 2004, the U.S. implemented special restrictions that made it even more difficult.