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Convicted serial killer Lonnie Franklin Jr. has died on death row in California's San Quentin State Prison, authorities said Sunday.

Franklin, 67, dubbed the "Grim Sleeper," was found unresponsive in his cell Saturday night and was pronounced dead at 7:43 p.m., the state Corrections Department said in a statement.

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The cause of death wasn't immediately clear, and there were no signs of trauma, the department said.

Franklin, a former mechanic and garbage man, was convicted in 2016 of the murders of nine women and a teenage girl in Los Angeles from 1985 to 2007. After a three-month trial, he was sentenced to death.

Franklin's moniker derived from what authorities believed was a break of more than a decade in his killings. He was convicted of murdering seven women from 1985 to 1988; the others were killed from 2002 to 2007.

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Many of Franklin's victims were poor and black. Their bodies were found in alleys, bushes and trash cans. Authorities suspected him of several more killings, although prosecutors said he wasn't charged with additional murders because of the long time it took to bring his case to trial.

He was arrested in 2010 after years of pressure from local activists, and a cold case task force used DNA evidence to connect him to the murders.