Allegheny County emergency dispatchers say they were called at 1:17 p.m. Sunday about the threat found at the Mall at Robinson. Robinson Township is a Pittsburgh suburb.
Officials say the note found in a dressing room at the Sears department store implied that three explosive devices were present.
Police, fire and ambulance units responded, in addition to the county bomb squad and bomb-sniffing dogs. No injuries were reported.
The mall's marketing director says the mall, which had been scheduled to close at 6 p.m., will remain closed as authorities investigate.
In February, a threat on a bathroom wall prompted the evacuation of another suburban mall in nearby Ross Township.