A four-CD box set of previously unreleased songs by Tom Petty and the Heartbreakers titled An American Treasure, is set for release on Sept. 28.

The collection is the first posthumous album for Petty who died in October at the age of 66 from an accidental drug overdose.

An American Treasure will contain 60 tracks spanning unreleased studio recordings, live recordings, deep cuts and alternative versions of famous Petty songs, Rolling Stone reported, citing an announcement made on SiriusXM radio.

Petty's wife Dana and daughter Adria help put the collection together along with former Heartbreaker members Benmont Tench, Mike Campbell and studio collaborator Ryan Ulyate.

A two-CD version of An American Treasure will also be released.

A song from the set titled "Keep a Little Soul," was released Wednesday alongside a music video featuring archival footage of Petty and the Heartbreakers.