Anthropic notified authorities earlier this week and said an automated testing process was responsible for the submission, according to the police.
The fast-advancing technology has become a matter of keen national interest amid reports of AI agents hacking into corporate computer networks, and warnings from researchers that it could one day pose an existential threat to humanity.
In September, Anthropic rival OpenAI apologised for the hacking of an Australian health data portal by a rogue AI agent, the first known instance of an AI agent exploiting a government website.
Previous incidents have involved AI agents hacking into vulnerable systems or commandeering unsanctioned platforms to communicate with one another. This is the first known case in which a rogue AI appears to have tried to communicate a bogus tip to authorities.
The Philadelphia police department said the tip "was flagged as spam and was never forwarded to the Real-Time Crime Centre for investigative vetting or dissemination."
It added that Anthropic had told them the company intended to publish a report on the incident.
Anthropic did not immediately respond to a request for comment.
Pennsylvania law specifies it is generally a misdemeanour crime for "a person" to knowingly give false reports to law enforcement authorities. This includes "information relating to an offence or incident when he knows he has no information relating to such offence or incident."
Police quoted Anthropic as telling them the testing process was stopped after the incident was uncovered.
The false tip was submitted through PhillyUnsolvedMurders.com concerning an unsolved homicide. The tip, dated July 18, 2026, purported to come from someone who might have information about the case, the police said.
Police said they did not have evidence of unauthorised access to their systems or compromise of police department data.
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