US outlet CBS News reported Petty's death, citing Los Angeles law enforcement officials.
The singer-songwriter, known for hits such as "American Girl" and "I Won't Back Down," was reportedly hospitalized on Sunday after suffering a heart attack.
According to TMZ, citing law enforcement sources, Petty was found unconscious at his home in Malibu, California, on Sunday. The singer was reportedly rushed to hospital, where TMZ later claimed "a decision was made to pull life support."
Courtney Love, Talib Kweli, Kid Rock and Cyndi Lauper were among many stars posting remembrances online.
The musician's family and representatives have yet to confirm or comment on those reports.
Tom Petty had just last week wrapped up his latest tour, marking the 40th anniversary of his band, Tom Petty and the Heartbreakers.
dm/gsw (Reuters, AP, AFP)