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Police have arrested 10 people in the U.K., Belgium and Malta for allegedly hijacking mobile phones belonging to U.S. celebrities including internet influencers, sports stars and musicians to steal personal information and millions in cryptocurrency, authorities said.

The European Union police agency Europol said Wednesday that the gang is believed to have stolen more than $100 million in cryptocurrencies by using so-called SIM swap attacks.

These attacks involve deactivating a victim's SIM card, either by tricking the or using a corrupt insider, so that the number can be transferred to another card under the gang's control.

The arrests were the result of a joint investigation by U.K., U.S., Canadian, Belgian and Maltese police, Europol said.

Europol didn't specify the nationalities of those caught in the sweep, but the U.K.'s National Crime Agency said a day earlier that eight men were arrested in England and Scotland. Two others were arrested previously in Belgium and Malta, Europol said.

Neither agency identified the celebrity victims.

Investigators found that after accessing victims' phone numbers, they were able to take control of apps or accounts by requesting password reset codes sent via SMS. Then they were able to steal money, cryptocurrencies and , including contacts synced online, as well as hack into and post from , Europol said.

Europol has warned that SIM swapping is a growing threat carried out by fraudsters.