Students were told: “Run Hide Fight” in a tweet, as police rushed to the scene at around 10am local time.
Of the seven people being treated in hospital, two are in a stable condition but there are no details on the other five, the fire department said.
Local reports said SWAT teams and other armed police are on campus in Columbus as officers on loud speaker are warning students that the gunman is at large.
Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College.
— OSU Emergency Mngmnt (@OSU_EMFP) November 28, 2016
The university’s Emergency Management urged people on campus to “wait for police officers directions” and to contact police only with information.
“Run, hide, fight” is standard protocol for active shooter situations, meaning: “Run”, evacuate if possible; “Hide”, get silently out of view; or “Fight”, as a last resort, take action to disrupt or incapacitate the shooter if your life is in imminent danger.
With nearly 60,000 students at its main Columbus campus, Ohio State is one of America’s largest universities.