Most of the videos purportedly showing violations committed during the December parliamentary elections were "edited" and distributed online from the United States, investigators said Saturday, once again heating up anti-American rhetoric.

Federal investigators examined online videos that were posted to bolster complaints of fraud at polling stations Dec. 4.

They concluded that "most of them have elements of editing," the Investigative Committee's spokesman, Vladimir Markin, said in his official remarks.

"Notably, all the edited videos were distributed from a single server based in the United States, California," Markin said.

He didn't elaborate but added that Russian law enforcement is searching for those responsible.

YouTube and blogs were flooded with footage shot by people who said the images were eyewitness accounts exposing numerous cases of election fraud all over Russia during the Dec. 4 vote.

Official results showed that United Russia picked up 45 percent of the vote and a majority of seats in the State Duma.

But widespread suspicion about the accuracy of those results sparked public discontent and demands for new elections.

Protesters in several Russian cities turned out by the thousands Saturday to repeat those demands.

Many videos shot at polling stations were uploaded to YouTube, but Markin's announcement was short on specifics. It was unclear whether he was referring to the popular international video hosting site, which is based in California.

The examined videos were filmed in numerous parts of the country, including the Moscow, Kemerovo, Tyumen, Sverdlovsk, Tula, Krasnoyarsk and Saint Petersburg regions; the republics of Chuvashia and North Ossetia; and the cities of Moscow and Yekaterinburg, the investigators said in a statement.

Markin didn't mention how much footage was checked but said some of the images had been doctored.

He mentioned only one example, however, saying a video allegedly featuring vote-rigging at polling station No. 2943, located at Moscow's lyceum No. 7560, doesn't show the authentic interior of the premises and real members of the elections commission.

The investigators are not the first to question the credibility of the videos. In December, the head of the Central Elections Commission, Vladimir Churov, said the scenes were "movies" filmed by unknown camera operators at fake polling stations.

Lilia Shibanova, leader of the independent watchdog Golos, which reported the violations, called the investigators' statement part of the Kremlin's misleading campaign.

The officials "are trying to make people believe that the elections were fair, with minor violations, while all the accusations are provocation from the United States," Shibanova told The Moscow Times.

Amid the post-election outcry, Russian officials at all levels have intensified the vigor of their claims that the State Department sponsored the massive protests that followed the December elections.

U.S. officials have repeatedly dismissed the accusations.

Shibanova said the campaign to discredit the protests started shortly before the parliamentary elections when state-run NTV made a film about Golos accusing it of receiving financial support from the West.

"Such propaganda is aimed at those who are not Internet experts and don't know much about YouTube and video editing," she said.

The Investigative Committee could not be reached for comment Sunday.