SAN FRANCISCO — YouTube has changed its powerful search algorithm to promote videos from more mainstream news outlets in search results after people looking for details on the Las Vegas shooting were served up conspiracy theories and misinformation.

YouTube confirmed the changes Thursday. It didn't say how it decides which news sources are authoritative.

In the days after the mass shooting, videos abounded on YouTube, some questioning whether the shooting occurred and others claiming law enforcement officials had deceived the public about what really happened.

Searching for "Las Vegas shooting" on YouTube led many people to these videos, some of which claimed it was a "false flag," a term conspiracy theorists use to refer to mass shootings they believe were staged by the government to promote gun control.

Law enforcement officials say Las Vegas gunman Stephen Paddock acted alone, opening fire Sunday from the 32-second floor of the hotel. The attack killed 58 people and injured nearly 500. Paddock shot and killed himself as police tried to break into the room.

Jake Morphonios, who runs the End Times News Report, championed the theory of a second shooter on the fourth floor of the Mandalay Bay casino. He says he presented a "fact-based analysis of the evidence" and insists "there is nothing offensive in my videos." But Morphonios says he received a strike from YouTube for violating its community standards. YouTube takes down accounts that get three strikes in three months.

As a result, Morphonios told YouTube viewers he deleted all of the Las Vegas videos.

"I hated to do it, but if I get any more strikes, my entire channel is going to be deleted," he said in a video explaining the decision.

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Public outcry over YouTube videos promoting conspiracy theories is just the latest online flap for the major U.S. Internet companies. Within hours of the attack, Facebook and Google were called out for promoting conspiracy theories, with one anonymous message board misidentifying the shooter and claiming he was an anti-Trump Democrat.

Paddock's motives still aren't clear. He was a retired accountant with a taste for high-stakes poker. His brother, Eric Paddock, said he wasn't aware of any religious or political affiliations.

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This isn't the first time fringe content has plunged YouTube into controversy. Major brands pulled spending on YouTube earlier this year after reports surfaced that their ads were running next to extremist videos.

YouTube is one of the Internet's most popular destinations for video. People now watch more than 1 billion hours of videos a day on it.

Helping drive that popularity is the "Up next" column which suggests additional videos to viewers.

The Wall Street Journal found incidents this week in which YouTube suggested videos promoting conspiracy theories next to videos from mainstream news sources. YouTube acknowledged issues with the "Up next" algorithm and said it was looking to promote more authoritative results there, too.

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