A Bay Area jewelry store was hit Monday evening by nine masked thieves who smashed display cases with hammers, surveillance video shows. 

The robbery took place around 7:30 p.m. at the Iceberg Diamonds jewelry store inside the Sun Valley Mall in Concord. 

Jewelry store robbery.  (Concord Police Department)

The Concord Police Department released seven seconds of surveillance footage. 

The robbers-to-be can be seen entering the store and swinging hammers at the front display cases, which contained rows of jewelry. The glass shatters in fragments and the thieves reach inside to steal items. 

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Police said store employees tried to intervene and were kept back by the "hammer-wielding criminals." The thieves had left by the time police arrived. 

An interior view of Sun Valley Mall in Concord, California (Google Maps)

Customers thought they had heard gunshots but the noise was actually the sounds of the robbers’ hammers breaking glass, police said. 

The Concord Police Department told Fox News that it is alerting other law enforcement agencies in the area to see whether Monday night's robbery resembles any other crimes. 

Iceberg Diamonds jewelry store was not available for comment. 

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The case is being investigated by Concord Police Department Detectives. Authorities are asking anyone with information relevant to the case to contact Detective Christine Corey at 925-603-5828. 

Concord is about 30 miles east of San Francisco. 

FILE: A view looking up Taylor Street of the Tenderloin neighborhood in San Francisco.  (AP)

Monday night’s theft comes amid a wave of thefts and robberies in the Bay Area. In San Francisco, more than 150 families have hired private security to patrol their streets amid brazen property crimes. 

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As of Oct. 31, San Francisco police had received reports of 810 burglaries or attempted burglaries this year in the jurisdiction of the Mission District Police station – a 13% increase from the same time the following year, according to the San Francisco Chronicle

Fox News’ Cortney O’Brien and Emma Colton contributed to this report