The school district is on lockdown, district officials said.
Authorities say the incident is at Santa Fe High School.
The Santa Fe school district issued an alert Friday morning saying Santa Fe High School has been placed on lockdown. "We will send out additional information as soon as it is available".
"We thought it was a fire drill at first but really, the teacher said, 'Start running, '" the student told the television station.
Westwood One reports at least one student says she saw her friend get shot.
The eyewitness said students fled the school in a panic.
The Santa Fe school district posted a statement on their Facebook page Friday regarding the incident.
Houston-area media reported that the Harris County and Galveston County sheriff's offices were also sending deputies to the scene, and that a medical Life Flight was called to the school.
News chopper footage showed a small crowd of students emptying their backpacks for inspection on the grass.
The latest reports of a possible shooting at a USA school underscored a national debate over gun control and gun rights that intensified after an assailant killed 17 students and staff members in February at high school in Parkland, Florida. Santa Fe police swept the campus but found no threat.
Santa Fe PD and Galveston County Sheriff's department are both on the scene.