Cops blocked off a swath of Midtown Monday in response to bogus reports that a man perched atop a Midtown building with a rifle.

Someone called cops Monday afternoon saying a man was on the roof of 550 West 45th Street and with a long gun, but police confirmed it was a false alarm after flying over the building.

Cops closed streets within a roughly one-block radius of the building, which is at the corner of 11th Avenue, while they investigated.

At least one office building nearby was on lock-down.

“A coworker had managed to leave minutes before and called to tell us SWAT teams were coming down our block,” said Zach Job, who works in 545 West 45th Street. “Then [building management] made an announcement thru the loudspeakers that we couldn’t leave the building.”