Police say a U.S. jeweller foiled a heist by locking a woman claiming to represent a diamond buyer in a vault and calling 911.

The would-be robbery played out on March 18 at ECJ Luxe Collection in Boca Raton, Florida.

The Sun Sentinel reports 46-year-old Fatima Milanovic faces charges of grand theft and organised fraud.

Vladislav “Bobby” Yampolsky told police he sensed something wrong when Milanovic tried to buy 11 stones worth $6.7 million in a deal that had been in the works for weeks.

He told police she wasn’t carrying any tools to inspect the jewels and she insisted on wrapping the items in packing material she brought to the store. Police said Milanovic was released on $50,000 bond.