British police investigating the burglary of up to 70 safe deposit boxes from London's jewellery business district have given more details on 9 April of how the thieves managed to make off with valuables estimated to be worth up to £200m ($300m).

London's Metropolitan Police said there was no sign of forced entry from outside the building over the Easter weekend. Instead, there was evidence the thieves disabled the lift to access the lift shaft, which took them to the basement were the safe deposit boxes were located.

"They forced open shutter doors into the basement where Hatton Garden Safe Deposit is based and then made their way to the vault area. Once outside the vault area, they used a Hilti DD 350 drill to bore holes in the vault wall. This wall is 2m thick and is made of reinforced concrete," said detective chief inspector Paul Johnson.

He told a media conference that the vault is still a scene of chaos. Johnson said: "The vault is covered in dust and debris and the floor is strewn with discarded safety deposit boxes, numerous power tools. We are in the process of identifying the owners of the safety deposit boxes that have been interfered with."

Owners of the safe deposit boxes have been gathering outside the building for any information regarding their valuables. It has emerged some of them were not insured for their items. If the losses in the raid are confirmed to be £200m, it will be Britain's largest ever heist.

The last record heist in Britain was carried out at a Securitas cash depot in Tonbridge, Kent, in 2006 when robbers stole almost £53m in cash.

In 2000, police foiled a daring attempt to steal £350m worth of diamonds from a display at London's Millennium Dome in what could have been the world's biggest ever robbery.