STOCKHOLM (AP) — An outdoor sculpture by Swedish artist Lars Vilks has partly burned down in a fire that police are investigating as a possible arson.

Vilks is best known for a drawing of the Prophet Muhammad that enraged many Muslims in 2007 and sparked death threats from extremists.

Authorities said Thursday that a fire destroyed parts of another of his works called "Nimis," a seaside sculpture he made of driftwood in a nature reserve in southern Sweden.

Emergency services spokesman Mattias Johansson told Swedish broadcaster SVT that about one-fifth of the artwork had burned down.

Vilks, who lives in a secret location with police protection, told newspaper Sydsvenska Dagbladet that arsonists have tried to set fire to "Nimis" before and that he considers it "a brutal form of art criticism."