Authorities were investigating reports of shots fired Wednesday evening at Cal State San Bernardino, officials said.
Classes were canceled for the evening, while students and faculty were advised in a campus alert to shelter in place. No injuries have been reported.
At 10 p.m., university spokesman Joe Gutierrez said police officers were evacuating campus buildings and escorting students and faculty out, but he could not confirm that a shooting actually took place.
"We're still telling people to stay sheltered in place until you are actually told you can leave," he said.
It's unclear how many people were on campus at the time of the incident, but more than 20,000 students attend the school, he said.
"It takes a while," he said of the evacuation. "If everybody leaves at once it's going to be chaotic."
Investigators were searching the campus for one or more possible shooters. On Twitter, campus officials urged those stuck in classrooms to stay quiet and to block doors and windows with desks and tables.
"Do not try to leave campus," the school's Tech Support Center said on Twitter. "Do not call police dispatch at this time."
The incident was reported shortly before 6 p.m. near the Visual Arts building and the west parking structure.
10:20 p.m.: This article was updated with information about evacuations.
7:30 p.m.: This article was updated to reflect that no injuries have been reported and to include additional advice from officials to students on campus.