France, Oct. 20 -- The Louvre Museum in Paris was closed for a second day on Monday as police continued their hunt for the gang who stole priceless pieces of royal jewellery in a daring morning raid. France's Interior Minister Laurent Nunez on Monday said he would tighten security outside cultural institutions as a result.

Officials said a team of 60 investigators was working on the theory that the theft soon after the museum opened was planned and executed by an organised crime group.

The seven-minute heist on Sunday morning reignited a row over a lack of security in France's museums.

Justice Minister Gerald Darmanin admitted on Monday to security flaws in protecting the Louvre which houses the Mona Lisa as well as an array of esteeme...