A gun was found below a toilet in a bathroom used by detainees inside NYPD’s 110th Precinct in Elmhurst on Thursday, according to police sources.

The rusty gun, discovered by a building maintenance worker, was inoperable due to the disintegration of the slide and a broken trigger.

The .32-caliber weapon was found with a magazine with four rounds loaded inside, police sources said.

Photos obtained by The Post show the handgun, weathered from humidity, apparently stowed below a toilet in a small cranny beside the drain pipe in a narrow bathroom stall.

Police have no clue how long the gun had been below the toilet, but have launched an investigation, according to police sources.