The entire school district is on lockdown, district officials said.
The incident occurred at Santa Fe High School around 8 a.m. CDT and officers were on the scene.
Santa Fe Independent School District posted on its website that the high school has been placed on lockdown.
Law enforcement officials were responding to reports of an active shooter at Santa Fe High School in Santa Fe, Tex., on Friday morning. It said it would send out more information as soon as it was available.
Galveston County Sheriff Henry Trouchesset said authorities are still trying to determine if there is more than one shooter.
"We were all standing (outside), but not even five minutes later, we started hearing gunshots", she said.
Students are telling FOX 26 that a random fire drill went off and then several shots were heard. Life Flight has been called to the scene. This is an unconfirmed report. She said students escaped through a door at the back of the classroom.
According to a law enforcement official, the Federal Bureau of Investigation is responding to offer assistance, CBS News senior investigative producer Pat Milton reports. Santa Fe police swept the campus but found no threat.
Santa Fe is a city of about 13,000 people roughly 30 miles southeast of Houston and 20 miles northwest of Galveston.