The British Museum has fired a staff member on suspicion of looting jewels from a storeroom and started a review of its security practices, the museum announced Wednesday.

The worker, who has not been named, stole or damaged items including gold jewelry and “gems of semi-precious stones and glass” dating from the 15th century B.C. to the 19th century A.D., the museum said in a news release.

London’s police force said in a statement that it was conducting an investigation, but that there had not been any arrests and that its “enquiries continue.”

Because of the police investigation, the museum would not comment on the value of the missing items or give any more details about them, a museum spokeswoman said in a telephone interview. The museum said that the majority of the items were small pieces kept in a storeroom. None had recently been on public display, the museum said, adding that “they were kept primarily for academic and research purposes.”

George Osborne, the museum’s chair, said in the news release that the museum was now working to recover the items and would “do whatever it takes, with investment in security and collections records, to make sure this doesn’t happen again.”

“It’s a sad day for all who love our British Museum, but we’re determined to right the wrongs and use the experience to build a stronger museum,” Osborne said.

The thefts are far from the first at the London institution. In 2017, the museum announced that six years earlier it lost a diamond Cartier ring worth almost a million dollars. In 2004, 15 pieces of Chinese jewelry were stolen in opening hours, while in 2002 a 2,500-year-old Greek marble head was taken from atop a plinth.

Wednesday’s announcement comes just over a week after a man was wounded in a stabbing outside the museum, leading to the tourist attraction being evacuated.