Sheriff Adrian Garcia says three people have been detained.
"All the victims and all the persons of interest were students of Spring ISD. There has been some information that this may have been gang-related."
Sheriff Garcia says the injuries are stabbings.
Spring ISD Superintendent Ralph Draper offered condolences to the families of those students involved.
"Every parent sends their child to school believing that school should be one of the safe haven places — a place where they can send them and receive them back at the end of the day. And it's what we spend our night and days working toward and it's what I lose sleep over. In my nearly 30-year career this is the one thing you pray never to experience, because we go into this business to make life better for children."
Superintendent Draper says the district will communicate with parents about plans for resuming classes.
Again Sheriff Adrian Garcia:
"We have three persons of interest that our investigators are interviewing and conducting the investigation at the moment. Be believe that a confrontation of some sort occurred around this, you know, 7:10 a.m. this morning that ultimately led into a physical confrontation that then produced weapons."
The school was under lockdown, but Spring ISD Superintendent Ralph Draper says parents are picking up students this hour.
"So parents, please know that we will flooding you with communication now and we will communicate to you what will happen at the balance of this day. We will also communicate with you when we will re-establish class here at Spring High. So you will be getting significant communication from this point."
Superintendent Ralph Draper says the school went into lockdown after the stabbings, shortly after 7 a.m.
"Priority number one was the security of the rest of our children, to make sure that we re-establish a safe and secure environment. To make sure that no one was still a threat. To make sure that there were not weapons. So it was our aim to re-establish a safe and secure place for all of the nearly 3,000 students who remained on campus."
The school is in the district of Congresswoman Sheila Jackson Lee, who issued her condolences, saying she's sure the community of Spring ISD will do whatever they can in the coming days to ease the pain, tensions and concerns of all affected.