Culver City Police Sergeant Dan Sukal says the theft at The Culver Studios was reported on Thursday.
On its website, the band offered a "no questions asked" $7 500 reward for information leading to the return of the instruments.
The stolen guitars include Petty's blond 1967 12-string Rickenbacker and his Gibson SGTVJunior, Mike Campbell's blue Dusenberg, Ron Blair's Fender Broadcaster and Scott Thurston's 1967 Epiphone Sheridan.
The band is known for a string of hit singles such as American Girl, Don't Do Me Like That, and Breakdown. Their tour kicks off on April 18 in Broomfield, Colorado.