A trio of armed and masked robbers barged into a Tiffany's in San Francisco and made off with a stash of diamonds Wednesday, the latest in the city's recent string of brazen heists of precious loot, police said.

Three armed robbers dressed as construction workers entered the Tiffany & Co. jewelry store at the Westfield San Francisco Centre at 865 Market Street around 3 p.m. and ordered everyone in the store to get down on the ground, according to police.

The trio forced an employee to open jewelry cases and made off with a stash of diamonds, police said.

Witnesses told police the three wore facemasks, reflective work vests, blue jeans and T-shirts that made them look like construction workers.

Nobody was harmed during the robbery, according to a statement from Westfield management.

"We are working closely with the San Francisco Police Department in their investigation of the incident," the statement said. "The safety of our guests and those who work at the Centre is paramount, and always a priority."

Westfield management said the mall was not locked down during the incident. Only the Tiffany's store was affected.

John Stier told NBC Bay Area his daughter was working inside the store during the robbery.

"I'm just relieved that she's OK. She told me she's OK on a text, and that's all I got from her," he said.

The investigation is still ongoing, police said.

Anyone with information is asked to call the SFPD anonymous tip line at (415)-575-4444.

Wednesday's heist is the latest in a slew of brazen robberies in San Francisco over the last two months.

Last week, thieves smashed a stolen SUV through the front entrance of the Wells Fargo History Museum and got away with historic gold nuggets. The Patagonia store near Fisherman's Wharf was the target of a smash and grab burglary in January after two men slammed a U-Haul van through its front door and took off with hundreds of dollars worth of jackets.

On Aug 15, 2013, the Walnut Creek Tiffany's store was hit by a pre-dawn heist. Four men rammed a stolen pickup truck into the store, taking off with a small bag of merchandise.

NBC Bay Area

NBC Bay Area's Terry McSweeney contributed to this report.