Democratic Rep. Karen Bass has grabbed the lead over billionaire businessman Rick Caruso in the hotly contested Los Angeles mayoral race, but there are still hundreds of thousands of votes to be counted. 

The latest returns from the Los Angeles County Registrar's Office show Bass up by 4,384 votes, leading Caruso, a former Republican, with 289,782 votes (50.4%) to 285,398 votes (49.6%). 

But nearly 40% of the ballots remain uncounted, and the race remains too close to call. Voter turnout is estimated to be about 27%, according to the Registrar's Office. 

Los Angeles County election officials on Friday estimated there more than 800,000 ballots that need to be counted. Those include about 790,000 vote by mail ballots, 21,000 conditional voter registration ballots, and 300 provisional ballots. 

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LA mayoral candidate Rep. Karen Bass

Rep. Karen Bass speaks during the Los Angeles mayoral debate at the Skirball Cultural Center in September. She ran against Rick Caruso in the midterm elections (Allen J. Schaben/Los Angeles Times)

"The number of outstanding Vote by Mail ballots may increase as the RR/CC continues to accept ballots that are postmarked by Election Day and received through Tuesday, November 15," the county clerk's office said. "These ballots are not included in the estimate." 

Though Bass, a progressive congresswoman, is favored to win in the traditionally far-left city, Caruso has attracted several celebrity endorsements after pledging to change how the city approaches crime and its homelessness crisis. Actor Chris Pratt, Kim Kardashian, Katy Perry, Elon Musk and others had endorsed Caruso in the months leading up to the election. 

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Los Angeles mayoral candidate Rick Caruso rallies the crowd at his election-night headquarters on Nov. 8 in Los Angeles.

Los Angeles mayoral candidate Rick Caruso rallies the crowd at his election-night headquarters on Nov. 8 in Los Angeles. (AP/Marcio Jose Sanchez)

According to government records, Caruso was a Republican for over two decades before becoming an independent in 2011. Caruso changed back to Republican in 2016 — a year when he served as California campaign co-chair for Republican John Kasich’s presidential bid — and then to independent again in 2019. He became a Democrat shortly before entering the mayoral race in February.

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Los Angeles election officials sort ballots.

Ballots are received, sorted and verified at the Los Angeles County ballot processing facility in Industry, California.  (Robert Gauthier/Los Angeles Times)

Bass is a six-term congresswoman representing California's 37th Congressional District. She was endorsed by former President Barack Obama, as well as Steven Spielberg, Julia Louis-Dreyfus, Danny Trejo and former LA Mayor Antonio Villaraigosa. 

Fox News' Tracy Wright contributed to this report.