CHICAGO - The FBI and police in Michigan are investigating a fire that was intentionally set three weeks ago outside the summer home of Chicago Mayor Richard Daley.

The fire did not damage the Daley home, but it did destroy a neighboring house and severely damaged another. No one was in any of the homes during the fire.

The fire occurred shortly after Daley received a threatening letter, said Berrien County Sheriff Paul Bailey. He told WGN-Television the letter indicated the writer was upset over the April 14 shooting of a cougar on the streets of Roscoe Village in Chicago.

Authorities said they do not have a suspect in the arson and it was not clear whether the person who wrote the letter was responsible for the blaze.