P ARIS -- As the alarms sounded at the Louvre Museum on Sunday morning, four suspects took off on two motorbikes, winding their way through central Paris, allegedly carrying with them a haul of "priceless" jewelry once worn by queens and royals.

French authorities are investigating after a robbery at the Louvre museum in Paris saw a group of thieves get away with "priceless" jewellery on moped this morning. Large numbers of tourists who wanted to see the Mona Lisa had their plans thwarted, after the Louvre said it would stay closed for "exceptional reasons".

The Louvre will remain closed for a second day running on Monday, management told the Agence France-Presse, after thieves stole crown jewels from the museum in Paris a day earlier. "The museum is not opening today,

Museum security concerns rise after the latest Louvre robbery, as experts recall other major art thefts, including the Isabella Stewart Gardner Museum's still-unsolved heist from 1990.

In that sense, the Louvre heist wasn’t really art crime, Vernon Rapley, a former leader of the London police force’s art squad, told my colleague Alex Marshall. It was “commodity theft.”

Thieves used a truck-mounted furniture elevator and angle grinders to access a second-floor gallery while visitors and museum employees watched them steal some of France’s crown jewels.

Paris Prosecutor Laure Beccuau says thieves who stole priceless jewelry from the Louvre Museum in a seven-minute heist may have been hired by a collector.