PHILADELPHIA (AP) — A two-alarm fire that damaged the building where the “Sound of Philadelphia” was born has been ruled an arson.

Fire officials say the Sunday morning blaze on the third floor of the Philadelphia International Records building has been determined to be “incendiary.” One man has been questioned and released.

Officials say the fire melted gold and platinum records and destroyed memorabilia but spared the studio. The company’s 10,000 master recordings are stored at an underground vault.

The company produced many R&B classics of the 1960s and 1970s. Michael Jackson, Patti LaBelle and Teddy Pendergrass are among musical luminaries who have recorded there.

Producers Kenny Gamble and Leon Huff said in a statement Tuesday that some lost items are “irreplaceable” but vowed to rebuild.