Investigators were told Epstein had been using heroin, said Maj. Ron Madrid of the Santa Fe County Sheriff’s Department.

Epstein, 47, a Tesuque resident, was driven to St. Vincent Hospital by his girlfriend, who described him as “under distress.” He died Sunday.

Epstein had been taking antibiotics for an illness, according to friends, and had recently suffered from flu, stomach problems and an abscess on his leg.

“He was at a friend’s house,” Madrid said. “Apparently he passed out in the bathroom, and (his girlfriend) drove him to the hospital.”

The state Office of the Medical Investigator had not determined a cause of death Monday.

Epstein has been a respected musician and producer for more than 20 years. In addition to his work with Petty, he played on some of Bob Dylan’s albums in the 1980s and produced a Grammy-award winning album for folk singer-songwriter John Prine called The Missing Years.

He was singer Carlene Carter’s longtime boyfriend, producing two of her albums, one of which was nominated for a Grammy.

“I’m devastated,” Carter told the Santa Fe New Mexican in a telephone interview. “I loved him very much. My kids thought of Howie as their father.

“We had a good life together for 15 years. We’ve been apart since May last year, and all I know is I’m going to miss him very much.”

A spokesman for the California-based MSO publicity firm, which represents Tom Petty and the Heartbreakers said, “The band is saddened by the news.”

Epstein’s last performance with the Heartbreakers was last March in New York during Petty’s induction into the Rock and Roll Hall of Fame. He was later fired from the band.

“We are deeply saddened at the news of Howie’s passing. It’s difficult to put into words how much we loved him and will miss him. The world has lost a great talent and a kind and gentle soul,” according to a statement on Petty’s Web site.

Epstein lived for several years with Carter – stepdaughter of country singer Johnny Cash and daughter of June Carter Cash – in a house in Tesuque.

The couple was arrested in June 2001 in Albuquerque with 2.9 grams of black-tar heroin and drug paraphernalia in a vehicle that had been reported stolen.

Epstein was not charged in that case. Carter, who now lives in Nashville, pleaded no contest to a charge of heroin possession and was sentenced to 18 months’ probation. Several months before the plea, Carter was released into the custody of her daughter, Tiffany Lowe, in Nashville.

Epstein, who was born in Milwaukee, Wis., is survived by a daughter, Jamie Leffler, 15, in Los Angeles, and two brothers in Milwaukee.