The Brooklyn Free Store was torched on March 19 after an arsonist had tried to burn it down on two previous occasions, investigators said. The FBI's Joint Terrorism Task Force has been called in to assist FDNY arson investigators because of the possible ALF connections, officials briefed on the case said.
The Animal Liberation Front is considered a violent extremist group by the FBI and US Justice Department.
ALF followers have engaged in illegal actions and sabotage in pursuit of "animal liberation."
ALF activists in the past have tried to forcibly remove animals from research laboratories, even conducting sabotage and arson in the name of animal rights.
Law enforcement officials would not say why the Brooklyn Free Store may have been targeted by someone with alleged links to ALF.
Spokesmen for the FBI and FDNY declined to comment.
Nobody was hurt in the three separate arson attempts along Walworth Street and DeKalb Avenue.
No suspect has been arrested.