Quantities of gems and cash were stolen from a safe deposit company in Hatton Garden over the four-day Easter holiday.

John Collins, 74, Daniel Jones, 58, Terence Perkins, 67, and Brian Reader, 76, each pleaded guilty to conspiracy to commit burglary during a hearing Friday at Woolwich Crown Court.

Three more defendants -- Hugh Doyle, William Lincoln and Jon Harbinson -- denied conspiracy to commit burglary and will face trial starting November 16.

They also face a charge of conspiracy to convert or transfer criminal property between April 1 and May 19.

Prosecutors decided not to pursue that charge against the four defendants who entered guilty pleas Friday.

Police haven't given a precise value for what was taken from the vault of Hatton Garden Safe Deposit Ltd.Estimates reported by British media at the time ranged from hundreds of thousands of pounds to £200 million, or $300 million.

Investigators said the thieves appeared to have gained access to the basement vault through an elevator shaft, using a drill to bore through a 6-foot wall to reach the safe deposit boxes.

Following the raid, the Metropolitan Police Service said it was examining why the force did not respond despite being made aware a burglar alarm had gone off at the premises on April 3.

How a heist is masterminded