Harris County Sheriff's Department Maj. Armando Tello said "a person of interest" had been detained, ABC News reported.
Student Brittany Mobley said two males were arguing when one pulled a gun and started shooting, KHOU-TV, Houston, reported.
"I saw two dudes basically get into an altercation and the dude that shot, he basically got angry and started shooting the other guy," she said.
The man involved in the argument was one of those wounded, witnesses said.
Citing witnesses, KHOU-TV said a male shooting victim was carried out of the library handcuffed to a stretcher.
Mark Zaragosa said he had just come out of an Emergency Medical Technician training class when he saw two shooting victims and attended them.
"The two people that I took care of had just minor injuries," he said.
Citing a federal law enforcement source it did not identify, CNN reported a fourth injury -- that of an unidentified person who suffered a heart attack.
The college was placed on lockdown following the shooting at about 12:30 p.m., school spokesman Jed Young told CNN.
"We know that shots have been fired and we are in a shelter-in-place situation on the campus," Lone Star College System spokeswoman Vicki Cassidy told the Houston Chronicle. "It's a pretty chaotic scene at this point in time."
The Chronicle said the shooting occurred in the library and also may also have occurred in a cafeteria.
KPRC-TV, Houston, reported the suspect being sought was described as wearing a red shirt and an Atlanta Falcons baseball cap, and was last seen running through a wooded area near the campus in an unincorporated area of Harris County.
More than 10,000 students attend the school.