LONDON- British police were hunting for a gang on Wednesday who raided safety deposit boxes in London's major jewelry business district, making off with cash and gems in what local media said could be the country's biggest-ever heist.

London's Metropolitan Police said the thieves used heavy cutting equipment to get into the vault at Hatton Garden Safety Deposit Ltd, where they are believed to have broken into 60 to 70 boxes.

According to the Sun newspaper, the gang are thought to have tunneled their way in through one wall to access a lift shaft at the building on Friday, while businesses in Hatton Garden, home to almost 300 diamond, gold and gem dealers and more than 50 shops, were closed for the Easter holidays.

They then abseiled down to the vault and smashed their way in, an unnamed source told the paper.

Police gave no details of what was stolen but the Sun said the haul could be as much as 200 million pounds ($300 million), dwarfing the amounts taken in Britain's previous biggest heists.

"Robbery at one of the biggest safe deposits in Hatton Garden over the Easter weekend," London gemologist Thelma West wrote on Twitter. "The loss is Huge."

She said a lot of jewelers and dealers leave their stock in safe deposits over holiday periods.

Diamond expert Lewis Malka, who owns a business in Hatton Garden, tweeted: "Big robbery at one of the safe deposits in Hatton Garden over the Easter weekend. Not good news for a lot of dealers."

On its website, Hatton Garden Safe Deposit Ltd said it was founded in 1954 and was one of the first companies in Britain to offer safe deposit boxes.