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A smash-and-grab robbery at a Riverside shopping mall on Sunday evening prompted a multi-agency response, police said, adding that initial reports of a shooting turned out to be unfounded.

A dispatcher with the Riverside police and fire departments told the Los Angeles Times that the agencies were notified of the incident at about 6:30 p.m. at the Galleria at Tyler, in the 1200 block of Tyler Street (map).

Officers arrived at the scene and determined that three male robbers had entered a jewelry store inside the mall and "started smashing the glass counters with sledgehammers," the Riverside Police Department said in a statement published on Facebook.

"The noise heard from the breaking glass was reported as gunfire," the post said.

Scores of law enforcement officers, including some from the Riverside County Sheriff's Department and the police departments of San Bernardino and Eastvale, descended on the mall and assisted in locking it down.

After authorities discovered that the robbers had fled the scene, officers were "searching the businesses to ensure the safety of all inside," the Riverside police statement said. No additional description of the trio was immediately available.

The episode prompted an outcry on social media, where conflicting reports initially described a possible "active shooter" or armed robbery at the popular retail destination.

Soon afterward, however, the head of a neighboring police agency said descriptions of gunfire were erroneous.

"Officers were called to Riverside Incident as a mutual aid - shooting call. Shooting unfounded," tweeted San Bernardino police Chief Jarrod Burguan, whose department had responded days earlier to a deadly shooting rampage at the Inland Regional Center in that city.

@SanBernardinoPD officers were called to Riverside Incident as a mutual aid - shooting call. Shooting unfounded. — Chief Jarrod Burguan (@SBPDChief) December 7, 2015

Multiple ambulances were seen in the Galleria at Tyler's parking lot Sunday night, but no injuries were reported.

A witness who was inside the mall at the time of the incident described a chaotic scene.

"I understood that they tried to rob a Robbins Brothers jewelry store," Eloy Medina, 42, said in an interview with The Times. "There were two definitely loud bangs which made all the shoppers on the first floor start running for their lives."

Another witness told KTLA that a Ben Bridge jewelry store had been robbed.