Police are investigating after a man was sent hate mail which claimed he was involved in animal testing.
Both the 50-year-old from Baston, Lincolnshire and his neighbours have received the letters alleging he works for Huntington Life Sciences.
Detectives said the man had been wrongly identified and has no connections with the laboratory.
The man is believed to have been targeted as part of a national campaign by animal rights activists.
Letters are being sent as part of a campaign aiming to disrupt the activities of the laboratory.
Det con Craig Morrison said: "The matter is being investigated as a hate related crime of harassment.
"The communication is part of a pattern of numerous anonymous letters from animal rights extremists being received by individuals indirectly associated with the medical research industry.
"These letters falsely accuse the recipients of criminal offences, including sexual offences."
The letters are being investigated under the Malicious Communications Act of 1988.