Photos Show How Burglars Drilled Through London Vault's Massive Concrete Wall

— -- The Metropolitan Police in London released photos today of a company vault that authorities believe took the burglars four days to break into, leading to a brazen heist.

The suspects drilled through the 20-inch thick concrete wall of the vault using a "heavy duty" Hilti DD350 drill, according to a police statement and images released today.

Metropolitan Police officials said they believe suspects entered the Hatton Garden safety deposit company in London's jewelry quarter on Thursday, April 2, around 9:20 p.m., then also on the following Friday, Saturday and Sunday at varying times. The hole, about 3 feet from the floor, is about 10 inches high and nearly 18 inches wide, police said.

"The vault was covered in dust and debris and the floor was strewn with discarded safety deposit boxes and numerous power tools, including an angle grinder, concrete drills and crowbars," Metropolitan Police said in a statement. There have been no arrests yet. Local media reports estimate the value of the goods stolen to be as much as $300 million to simply "hundreds of millions of pounds" of jewelry.

“Of the 72 boxes opened during the burglary, we have only been unable to make contact with six people who we believe have been a victim of crime," Detective Superintendent Craig Turner, head of the Flying Squad, said in a statement. "We continue to make efforts to trace them. ”

The safety deposit company is located in the basement of the building, which shares a communal entrance with other businesses, police said.

"There was no sign of forced entry to the outside of the building," police said in its statement. "The thieves disabled the communal lift on the second floor and then used the lift shaft to climb down into the basement. They forced open shutter doors into the basement and bored holes into the vault wall."

Police have recovered about 400 pieces of evidence, including items for DNA profiling and fingerprints, while digital forensic specialists have recovered thousands of hours of closed-circuit TV surveillance footage.

Police received an alarm call that Friday at around 12:21 a.m. after an intruder alarm was activated at the Hatton Garden safe deposit company, but "no police response was deemed required," the police statement read. An internal investigation is taking place about what happened.