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An unspecified number of gems were stolen from the Cleveland Museum of Natural History's mineral collection Thursday, a museum spokeswoman said.

(Plain Dealer file photo)

CLEVELAND, Ohio -- Detectives are investigating after several gems were stolen from the Cleveland Museum of Natural History.

An unspecified number of gems were stolen from the museum's mineral collection sometime Thursday afternoon, a museum spokeswoman said in a statement.

The gems are "not thought to be of significant material value," but their values have not yet been confirmed.

"The museum takes any possible security breach very seriously and is working with authorities on the investigation," the spokeswoman said.

Detectives from Cleveland and University Circle are investigating.

The museum is not releasing any additional information while the investigation is ongoing, the spokeswoman said Saturday.