Dutch police are responding to a spate of letter bombs despatched to workplaces throughout the nation as a part of a Bitcoin extortion plot.

On Thursday, a letter bomb prompted a small explosion at an ING Financial institution workplace in Amsterdam, Reuters reports. Simply hours earlier, authorities disarmed one delivered to an workplace of US tech agency Unisys, positioned close to Utrecht.

The incidents comply with the explosion of two letter bombs on Wednesday, one at ABN Amro financial institution’s Amsterdam mail-sorting workplace, and one other within the Kerkide mailroom of Japanese electronics agency Ricoh, near the Germany border.

Fortunately, no person was harmed in any case.

Bitcoin extortion plot tied to January’s letter bombs

Authorities mentioned Wednesday’s packages had not been equally labeled. They urged mail recipients ought to be cautious of thick white envelopes despatched with two stamps, and have a printed piece of white paper with the supply and return addresses in plastic hooked up.