Update 7.12pm: A man ploughed his car into a group of pedestrians at Ohio State University and then began stabbing people with a butcher knife before he was shot and killed by an officer, campus police said.
Nine people were injured, one critically, and Columbus Police Chief Kim Jacobs said police were looking into whether it was a terrorist attack.
— ABC News (@ABC) November 28, 2016
The details emerged after a morning of confusion and conflicting reports that began with the university issuing a series of tweets warning students that there was an "active shooter" on campus near the engineering building and that they should "run, hide, fight".
Ohio State Police Chief Craig Stone said the attacker drove over a kerb outside a classroom building and an officer who was nearby shot the driver.
"The threat ended when the officer shot the suspect," said Monica Moll, the school's public safety director.
At least two people were being treated for stab wounds, four were injured by the car and two others were being treated for cuts, university officials said.
— CNN (@CNN) November 28, 2016
Update 5.20pm: Ohio State University says a "shelter-in-place" warning has been lifted and the scene is secure following reports of an active shooter and at least seven people injured.
Ohio State tweeted today that all classes would be cancelled for the rest of the day.
The university had warned students in a series of tweets earlier that there was an active shooter on campus and that they should "run, hide or fight".
The Columbus Fire Department says seven people had been taken to the hospital. It says two of those people were in stable condition. It did not have details on the other five.
Hospital officials later said that eight patients they received from the scene have non-life-threatening injuries.
The eight patients were split among OSU Wexner Medical Centre, OhioHealth Grant Medical Center and OhioHealth Riverside Methodist Hospital.
Update 4.15pm: Nine people are believed to have been injured, one of them critically, after a gunman or gunmen targeted one of the largest universities in the US.
One suspected gunman has reportedly been shot dead at or near Ohio State University, with another suspect being sought by police. The university's students remain in lockdown.
The college has almost 60,000 students on its main campus. It is not clear how many were present on campus when the alert began this afternoon.
Update 4pm: Seven people have been taken to hospital after a shooting incident at Ohio State University, the fire department has said.
There is a report also of a body bag - an eighth casualty - on campus.
The Columbus Fire Department added that two of those people are in stable condition. It had no information on the other five people.
Ohio State University warned students in a series of tweets on Monday morning that there was an active shooter on campus and that they should "run, hide or fight".
One tweet says: "Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College."
Watts Hall is a materials science and engineering building.
The university followed up with another tweet: "Continue to shelter in place in north campus area. Follow directions of Police on scene."
The university also asked for anyone with information to call police.
"Run, hide, fight" is standard protocol for active shooter situations. It means: 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.
A Columbus police dispatcher declined to comment on the reports, but police vehicles were seen at the scene.
With nearly 60,000 students at its main Columbus campus, Ohio State is one of the nation's largest universities.
Update 3.40pm: Local reports are that up to seven people have bee taken to hospital after gunfire at one of the largest universities in the US.
There are also reports of a body bag on campus.
Five of those injured are reported to be in an unknown condition, with two in a stable condition.
The shooter is reported to still be active on the campus, with students advised to hide where they are, avoid the area if possible and fight the shooter as a last resort.
Reports are emerging of a shooting incident at a school campus in the US.
While it is not yet clear whether anyone has been injured, an active shooter is reported to be present on the campus of Ohio State University, one of the largest in the US.
People have been urged to shelter where they are and avoid the area.
Ohio State University has tweeted that an "active shooter" is on campus and students should "Run. Hide. Fight". Police are on the scene.
Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College.— OSU Emergency Mngmnt (@OSU_EMFP) November 28, 2016
CNN reports that student Wyatt Crosher said he heard gunfire that he believes came from a class building across the street.
"My roommate and I heard about three or four gunshots from across the street, and soon after we heard a bunch of police and ambulances pull up across the street," the 19-year-old said.
"We can't see the building where the shooting happened because of a dorm blocking our view. It truly sounded like gunshots, and really soon after we heard a bunch of sirens. We can see the police cars from our dorm."
Students at Ohio State University told to "run, hide, fight" after reports of an active shooter on campus. pic.twitter.com/EfozvRrq3W— Fox News (@FoxNews) November 28, 2016