With meticulous planning and remarkable good fortune, the thieves who broke into a safe in London's diamond district seemed to have pulled off the perfect jewel heist. But their luck ran out on Tuesday when more than 200 Scotland Yard officers closed in on them.

Nine people were arrested in a triumph for embattled detectives whose early work had been criticized because of an embarrassing failure to respond to a midnight alarm at the start of a holiday weekend.

That delay gave the thieves more than 48 hours to carefully remove the contents of the safe used by jewelers in the Hatton Garden district.

The suspects, all British men aged 43 to 76, were questioned in a London police station after coordinated morning raids in northern London and the southeastern district of Kent, the authorities said.

According to Scotland Yard, bags containing significant amounts of high-value property were recovered at one of the addresses, but no monetary value was assigned to the heist.

The bold robbery over Easter weekend fascinated Britain. Dressed in fluorescent vests and hard hats, the thieves entered the high-security vault area in London's diamond district, carrying bags and wheeling garbage bins for carrying off the booty.

To gain entry, they climbed down an elevator shaft and drilled through concrete walls that were 2 meters thick, later making off with the contents of 72 safe-deposit boxes.

Commander Peter Spindler on Tuesday defended the police performance in the face of the earlier criticism.

"These detectives have done their utmost to bring justice to the victims of this callous crime," he said.

Nonetheless, police took the unusual step of apologizing for mishandling the alarm.