By Brad Segall

KING OF PRUSSIA, Pa. (CBS) — Police in Upper Merion are investigating a smash-and-grab robbery at a high-end watch store in the King of Prussia Plaza, a robbery that officials say lasted all of about 20 seconds.

Police are hoping that someone who may have been near the Tourneau store around 2:45pm Wednesday afternoon saw something that can help them solve the crime.

According to investigators, three black males entered the store with a small sledgehammer and threatened a security guard before smashing a display case and grabbing more than a dozen high-end watches worth hundreds of thousands of dollars.

So far they have only a vague description of the thieves.

“Right now we have men that were dressed in baggy clothing with their faces covered — we’re getting that from both witnesses and from reviewing surveillance video,” police sergeant Jeff Maurer tells KYW Newsradio.

And Maurer says it appears they know what they’re doing.

“Yes — they’re in, they move rather quickly, they go right to the high-end display case, and they’re in and out within a short period of time.”

Maurer says the trio fled through a service corridor to a parking garage in the rear of the plaza.  He says no injuries were reported and no weapons, other than the sledgehammer, were displayed.

Police have also reviewed surveillance from other areas of the mall as they attempt to identify the robbers.

It’s at least the third time this store has been ripped off for luxury wristwatches in little more than a year.  Last April, the store was hit by five bandits wielding hammers (see related story), and the previous July a group of three thieves — also with hammers — made off with more than a half-million dollars in merchandise (another related story).

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