Three men are dead and four others hospitalized in what police in Pittsburgh are calling a mass drug overdose.

All seven victims appear to have taken the unspecified drugs at the same time in a South Side apartment — and all wore an orange wristband that police said was likely given to patrons at a local venue.

Five of the victims were found in the apartment, one in the elevator, and the seventh on a nearby street — likely heading to or from the apartment.

“To be clear, this was not a case of a tainted drug being passed around or distributed in large volume at a large venue which could have affected even more people,” police said in a statement Sunday. “It appears to have been isolated to a single location.”

The first call came in around 2 p.m., police said, when a man was found unconscious on a city street and rushed to the hospital.

Not long after another call came in about an unconscious man in the elevator at The City Apartments on Tunnel Boulevard, who was pronounced dead at the scene, the Tribune-Review reported.

Then, just before dawn, five more victims — two dead and three unconscious — were found inside an apartment inside the same building — also due to unknown causes.

“The common factor between all these patients is that they were wearing orange wrist bands,” Pittsburgh Director of Public Safety Wendell Hissrich said at a Sunday morning briefing.

“Currently we know of two venue sites in separate locations throughout the city that were utilizing orange wristbands and that is providing us some investigative avenues to determine what’s going on with these victims,” Hissrich said.

“We are looking into all avenues at this point,” he added.

He would not identify the venues in question. He said all of the victims were men between the ages of 30 and 50, but would not provide more details.

Hissrich said the apartment building is not considered the source of the mysterious illnesses.

Police Commander Jason Lando told the Tribune-Review that the incidents are believed to be drug-related and tied to the event or events the victims attended.

“We do believe that these were overdoses that took place,” Lando told the paper. “At this time we have not identified the exact substance that was overdosed on.”