Multiple people were killed on Friday in a shooting at a high school in Santa Fe, Texas, CNN reported, in the latest gun violence in a country still shaken by the massacre at a Florida high school in February.

Citing unnamed sources, CNN said there were multiple fatalities after the shooting at the school about 48 km southeast of Houston.

The sheriff's office for nearby Harris County said its deputies were assisting with a "multiple-casualty incident."

"This is no longer an active shooting situation and the injured are being treated," the sheriff's department said on Twitter.

The school district in Santa Fe, said the situation was "active, but has been contained." Local media reported that a suspect was in custody.

US President Donald Trump wrote of the shooting on Twitter: "Early reports not looking good. God bless all!"

The latest such incident at a US school underscored a national debate over gun control and gun rights that has intensified after an assailant killed 17 students and staff on February 14 at Marjory Stoneman Douglas High School in Parkland, Florida.