(CNN) -- Two people were in critical condition Tuesday after a stabbing incident at a Texas college, a sheriff said.
Authorities have detained the suspect, an approximately 21-year-old male enrolled at the school, Harris County Sheriff Adrian Garcia told reporters.
Garcia said a call came in to 911 Tuesday morning describing a "male on the loose stabbing people" at the Lone Star College's CyFair campus.
Fourteen people were injured in the incident, Garcia said.
It was unclear what the suspect's motive was, or what weapon he used, Garcia said. The investigation is ongoing, he said.
"We do not know exactly what type of weapon was used other than to say that it is at this point an unknown instrument," he said. "We don't know whether a knife or some other type of instrument."
Student Maya Khalil, 19, was in class in the campus' health sciences building when the incident happened, she said. She managed to take photos of the chaotic scene as it unfolded.
"It was really scary," Khalil said.
The school was on lockdown Tuesday afternoon while authorities combed the campus to ensure no other injured people or attackers were there, Harris County sheriff's spokesman Alan Bernstein said.
Marianna Sviland, a teacher at the college, told CNN at 2 p.m. (3 p.m. ET) that students and staff were being allowed to leave campus.
Bernstein said it wasn't clear whether all of the injured people were stabbed.
"It's possible other people were running away" and became injured that way, he said.
Four people were taken to a hospital by helicopter, authorities said. The conditions of the victims weren't immediately available.
The four flown to a hospital "were in a dire enough situation that they were taken out on helicopters," Bernstein said.
Bernstein said it will take time for authorities to go through the campus and "make sure there (is) not another suspect or suspects."
"I do believe the confrontation was limited to a few (classrooms) or just one classroom -- not anybody roaming around and getting into a large number of areas," Bernstein said.
Details about what led to the incident weren't immediately released.
"Stay away from the area. Seek shelter in a secure location until the incident is resolved," the school posted on its website.
Tuesday's incident comes more than two months after three people were wounded in a shooting at a different Lone Star College campus -- the North Harris campus in Houston.
CNN's Catherine E. Shoichet, Greg Botelho, Paul Caron, Chuck Johnston, Ashley Fantz and Jason Hanna contributed to this report.
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