Detective Chief Inspector Paul Johnson of the London Metropolitan Police Flying Squad said the thieves appeared to have gained access to the vault of Hatton Garden Safe Deposit Ltd through the shaft of an elevator that is used by several businesses in the building.
The thieves disabled the elevator on the second floor of the building -- which would be the same as the third floor in the United States -- then climbed down the elevator shaft into the basement, he said.
Once there, he said, they used a drill to bore through a 6-foot-thick wall and gain access to the vault where the safe deposit boxes were.
Johnson said he had no figure for the value of what was stolen. A former police official in London has speculated that the loss could run to 200 million pounds, or 300 million dollars, in a remark widely reported by news media. And numerous British news organizations put the value of the loss in the hundreds of thousands of pounds. But Johnson said police were still identifying the owners of the ransacked safe deposit boxes and trying to contact them to learn what had been lost.
People with knowledge of the area have speculated that cash and jewels were probably taken. Some jewelry businesses reportedly stored some of their jewels in the boxes rather than leaving them in their stores over the holiday weekend.
Johnson said the scene in the vault remained chaotic as police continued their forensic examination. He said the floor was covered with dust and littered with safe deposit boxes and power tools.
Over the four-day Easter holiday, an unknown number of thieves broke into the vault and might have been able to take as much as four days to rifle through the boxes.
Johnson called the crime sophisticated and said there were a limited number of people in the UK capable of having pulled it off. He said had no idea whether the thieves were still in the country.
Although there was no sign of forced entry to the building, the detective said, "whether that involves inside knowledge will form part of the investigation."
Hatton Garden is a storied area in London and the heart of the city's diamond trade. The area's promotional website
says it is home to "the largest and most concentrated cluster of jewellery retailers in the UK" and has been for quite some time.
"History tells us that the old City of London had certain streets -- or quarters -- dedicated to specific types of business," the website says. "The Hatton Garden area has been the epicentre of London's jewellery trade since medieval times.
"Today, it maintains its international reputation as the centre of London's diamond trade. It is one of the finest and most renowned jewellery locations in the world."
The website of Hatton Garden Safe Deposit Ltd. says the company was founded in 1954 and offers a "secure and cost-effective solution to store and protect important and irreplaceable personal belongings."