"ATF Columbus Field Division is responding to reports of an active shooter at Wright-Patterson Air Force Base near Dayton, Ohio," ATF said in a Twitter alert.
Local police services are deployed to the base, located near Dayton in southwest Ohio.
The Air Force Base published a Twitter post saying that emergency responders, including security forces and firefighters, were responding to a "reported incident" at the hospital on the base.
"At approximately 12:40 p.m., base emergency responders (security forces, fire department) responded to a reported Active Shooter incident at the base hospital. Base personnel has been directed to shelter in place until the incident is investigated," Wright-Patterson Air Force Base said.
Local media reports said the shooter had barricaded himself on the fourth floor of the hospital.
