A man armed with an AR-15 breaks into an FBI office in Ohio and fires a nail gun at federal personnel.

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A man, who also carried an AR-15 assault rifle, entered an office of the Federal Bureau of Investigation (FBI) in Cincinnati, Ohio on Thursday morning and fired a nail gun.

He then fled in a car, sparking a shootout on an interstate highway, two law enforcement sources told NBC News.

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"At approximately 9:15 a.m. ET, at the FBI Cincinnati field office, a subject attempted to break into the visitor screening facility," the bureau said in a statement.

"Following the activation of an alarm and a response from armed FBI special agents, the subject fled north on Interstate 71," he added.

FBI offices in Cincinnati, Ohio.Google Maps

The Clinton County Emergency Management Agency warned of the closure of Interstate 71 in both directions in a section that includes five exits.

"Police exchanged gunfire with a suspect wearing a gray shirt and bulletproof vest," the agency said in a statement, warning people living nearby to stay on their cases and lock their doors.

Around 12:30 in the afternoon, the bureau reported that the subject was "contained", although it clarified that he was not yet in custody.

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Authorities are asking all residents and drivers within a one-mile radius of Center & Smith Roads not to leave or let anyone onto their property.

"Stay vigilant and if you are in the area, report any suspicious activity to 911," they asked.

This is a developing story.

Please check back for updates.