SANTA FE, Texas — Law enforcement responded to a high school near Houston after an active shooter was reported on campus Friday, with at least one student saying she saw a man with a gun enter her classroom and start shooting as the class evacuated.

The Santa Fe school district issued an alert around 8 a.m. saying Santa Fe High School was on lockdown. Galveston County sheriff's Maj. Douglas Hudson said units were responding to reports of shots fired, but said he had no immediate details on whether anyone had been hurt.

One student told Houston television station KTRK in a telephone interview that a gunman came into her first-period art class and started shooting. The student said she saw one girl with blood on her leg as the class evacuated the room.

"We thought it was a fire drill at first but really, the teacher said, 'Start running,'" the student told the television station.

The student said she didn't get a good look at the shooter because she was running away. She said students escaped through a door at the back of the classroom.

Authorities have not yet confirmed that report. Aerial footage from the scene showed students standing in a grassy field and three life-flight helicopters landing at the school.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives said it was responding to a shooting at the school.

There was a large law enforcement response to the same school in February when it was placed on lockdown after students and teachers said they heard "popping sounds." Santa Fe police swept the campus but found no threat.

Santa Fe is a city of about 13,000 residents located 30 miles (48 kilometers) southeast of Houston.