Unmasked thieves smashed open a glass display case with a hammer before stealing a diamond-encrusted necklace worth more than $4 million during a brazen daylight museum heist in Vienna, Austria on Thursday.

Austrian police say a manhunt is now underway for the two men, who posed as visitors to a jewelry exhibition at the Museum of Applied Arts (MAK) where the platinum necklace — featuring 673 diamonds and once owned by Egyptian royalty — was on display.

Police have released photos of the two suspects, who were captured by CCTV cameras before entering the exhibition. The pair is believed to have fled the scene on foot toward a neighboring park. Police said that no one was injured during the incident, although one of the suspects is thought to have been carrying a firearm.

In a statement, police added that “extensive search operations” are in progress, including the use of dog units. Interpol said that Austrian authorities have added the artifact to its database of stolen artworks.

The necklace was on loan from Van Cleef & Arpels, the French jewelry house that designed it for Egypt’s Queen Nazli in the 1930s. It was on show as part of an exhibition pairing items from the museum’s own collection with more than 300 of the maison’s designs.