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YouTube is modifying its search engine to "promote more authoritative sources" in an effort to demote debunked conspiracy theories that have been spreading in the wake of the Las Vegas massacre, according to The Wall Street Journal.

The Google-owned video-sharing service had been planning these changes prior to the mass shooting in Las Vegas on Sunday, but is speeding up its efforts to get them rolled out to prevent the spread of misinformation and respond to criticism about some of its search results, the Journal reported, citing an unnamed source close to the company.

One of those results in question was a video titled "Proof Las Vegas Shooting Was a FALSE FLAG attack—Shooter on 4th Floor," which claimed there were multiple shooters involved in the massacre — a rumor that has been refuted by authorities. On Tuesday, that video appeared as the fifth result when searching YouTube for "Las Vegas shooting," according to the report, helping it rack up more than 1.1 million views in just over a day.

"On Wednesday night, the company began promoting more authoritative sources in search results, especially for those about major news events," the Journal reported. There's no word as to how YouTube determines whether a source is authoritative.

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YouTube did not immediately respond to PCMag's request for comment.

Fake news about the shooting has also shown up on Google and Facebook. Google briefly surfaced a report from the anonymous message board 4chan identifying the wrong person as the shooter, the Journal reported on Monday.

"Within hours, the 4chan story was algorithmically replaced by relevant results," Google said Monday. "This should not have appeared for any queries, and we'll continue to make algorithmic improvements to prevent this from happening in the future."

Meanwhile, Facebook's Trending Topics surfaced posts from a Russian-backed news outlet stating the shooter had ties to a terrorist group, another claim authorities have refuted. Facebook removed the posts in question, but not before people took screen shots and circulated them online.

"We are working to fix the issue that allowed this to happen in the first place and deeply regret the confusion this caused," Facebook said.

This article originally appeared on PCMag.com.