Sources say a former MUFG Bank employee arrested on suspicion of stealing gold bullion from customers' safe deposit boxes has admitted to taking measures to avoid being discovered.

Tokyo police arrested 46-year-old Imamura Yukari on Tuesday on suspicion of stealing about 20 kilograms of gold bullion worth over 1.6 million dollars from two customers' safe deposit boxes at a branch in Nerima, Tokyo, last September. She is suspected of using spare keys to open the boxes.

The police said she has admitted to the charges. They continue to investigate, suspecting that she may have stolen money and gold totaling about 1.7 billion yen, or about 10.8 million dollars, from the boxes of at least 60 customers.

Investigative sources said Imamura had resealed the envelopes that the bank used to keep the spare keys in after taking the valuables from the boxes.

She told investigators that she thought the envelopes would be checked later so she opened them carefully.

She also said she intentionally shut down the system that operates the doors when customers came to the branch unexpectedly, and told them it was out of order to prevent them from accessing the room with the safe deposit boxes.

The police suspect that Imamura continued stealing for about four and a half years while taking measures to avoid being discovered, including replacing the stolen money and gold with some from the boxes of other customers.