The police have launched investigations after nine Japanese firms received threatening letters demanding money and containing a white powdery material, believed to be cyanide.
The letters demand a payment of 35 million won in bitcoins, failing which the toxic material may be used for indiscriminate killings.
"I will make fake medicine containing potassium cyanide and distribute it. Send 35 million won (USD 31,300) in bitcoins by February 22. If not, a tragedy will happen," local authorities quoted the letters as saying.
The names of the other two companies - another pharmaceutical company based out of Osaka and a food company - have not been revealed by the police, even though investigations are underway.
The letters were sent under different names, including that of executed Aum Shinrikyo cult leader, Shoko Asahara.
Shoko was executed in July last year, after being convicted of masterminding the deadly sarin gas attack on the Tokyo subway system in 1995, which killed over 10 people and wounded dozens, amongst other murders.
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