Nine firms, including drugmakers and a newspaper publisher, have received threatening letters demanding money and containing a white powdery substance believed to be highly poisonous cyanide, police have said.

The letters, sent under different names, such as Shoko Asahara, the executed Aum Shinrikyo cult leader, and others linked to organized crime, warned of potential indiscriminate killing using the toxic material, authorities said Saturday. The police are investigating the case as attempted blackmail.

Suspicious envelopes arrived at six pharmaceutical companies and the headquarters of The Mainichi Newspapers in Tokyo on Friday. They each had a message on an A4-size sheet of paper saying, “I will make fake medicine containing potassium cyanide and distribute it. Send 35 million won ($31,300) in bitcoins by Feb. 22. If not, a tragedy will happen,” the police said.

Two other companies — a pharmaceutical firm in Osaka and the Hokkaido branch of a Tokyo-based food company — also received similar letters the same day. The police declined to name the companies.

An official at The Mainichi Newspapers said the company had voluntarily submitted the letter to the police and that it will fully cooperate in the investigation.

The letters were also sent under the names of former senior members of Aum as well. Asahara, whose real name was Chizuo Matsumoto, was executed last July along with 12 former members of the cult after being convicted of numerous murders, including the 1995 deadly sarin gas attack on the Tokyo subway system.

The letters also carried different addresses, such as detention facilities in Tokyo.

The case follows a similar incident last year in which some pharmaceutical companies in Tokyo and Osaka Prefecture received threatening letters.