Officials held three students in connection with the stabbing at the Spring High School, which occurred around 7 a.m. Wednesday. The persons of interest were later taken to the Harris County Sheriff's office for questioning.
"We do believe the persons of interest we have in custody are the only persons of interest we need to have in custody," Harris County Sherriff Adrian Garcia said at a press conference Wednesday.
The stabbing happened after a confrontation in the school cafeteria, in which the victims were injured with "some kind of cutting instrument." Police have not yet recovered the weapon.
Two of the victims were transported to the hospital with minor injuries. Another victim, a 16-year-old boy, was flown by Life Flight to Memorial Hermann Hospital with stab wounds in his abdomen.
Hospital officials said the boy is in critical condition. He is expected to survive but will undergo surgery.
A 17-year-old student died in the school after being stabbed to death.
Spring High School was on lockdown for hours after the incident, as the school kept hundreds of parents away from the school.
"Every parent sends their children to school believing school should be one of the safe haven places they can send them and receive them at the end of the day," said Ralph Draper, superintendent for the school district. "In my 30-year career, this is the one things you pray never to experience."
In the aftermath of the stabbing, "our aim was to re-establish a safe and secure place for all of the nearly 3,000 students who remained on campus," Draper said. "We wanted to make sure no one else was hurt."
The school closed at 12:30 p.m., and students were picked up by buses and parents.