A former immigration officer says many illegal aliens can vote in national elections, in part because they can easily buy fake identification documents.

“I probably arrested more than a thousand illegal aliens in my career,” retired ICE Special-Agent-In-Charge Claude Arnold said during an interview with Fox News’ Bill O’Reilly. “I routinely encounter people in possession of voter registration cards… I would ask them, ‘Do you or have you voted?’ And often, I would get the answer, yes,” he said, adding that about 100 illegals told him that they had voted.

Illegals can vote because they can get realistic fake documents, he said.

“The demand is so great for counterfeit documents because the illegal alien population wants to work—that’s the majority of their motivation for wanting to come to this country,” he said. “So there’s a huge demand for those documents that are required to pass the employment eligibility verification procedures,” he added.

“In every neighborhood where there’s a significant illegal alien population, there are at least several document vendors who supply this service.” Illegals typically buy fraudulent documents in threes, he continued: A counterfeit resident alien card or work authorization card, plus a counterfeit California driver’s license, and a counterfeit Social Security card, which costs about $120 to $300.

Arnold’s interview comes after President-elect Donald Trump declared he would would have won the popular vote if millions who voted illegally were discounted.

Democratic Virginia Gov. Terry McAuliffe, a longtime ally of Hillary Clinton, ignored his state’s supreme court ruling and illegally gave 60,000 felons voter registration cards. Also, at least eight million adult illegal aliens are residing in the United States in defiance of the law.

The media did not investigate these claims, automatically declaring them “false” with much outrage and finger-wagging. Still, voting experts have told reporters at the Daily Mail that it’s likely illegal aliens, non-citizens, and other ineligible people, did vote in significant numbers on Election Day:

[E]xperts warn today that the rapid media condemnation of the president-elect is itself flawed—and that he was at the very least partially right in his claims. They said it is certain that—among other things—non-citizens were registered to vote and [did] cast ballots. It is also certain that there were other instances of illegal voting, including people who vote under false identities, and people who cast ballots in multiple states, which most attacks on Trump’s tweet chose to ignore, they warned… The most recent serious attempt to measure the number of non-citizen voters found that illegal voting is a widespread problem, although not as prevalent as Trump’s comments suggested. The 2013 study was conducted by Jesse Richman, a professor at Old Dominion University. The report was based on surveys by the Cooperative Congressional Election Studies in 2008 and 2010, which asked respondents for citizen status and whether they had voted. Based on the data, Richman estimated that 6.4 percent of non-citizens voted in the 2008 presidential election, which would translate to around 1.2 million votes. According to Richman, about 80 percent of these non-citizens voted for Barack Obama against John McCain. But the professor says his findings still wouldn’t account for Hillary Clinton’s entire 2.2 million lead against Trump in the popular vote.

These problems may have been compounded by the outgoing president himself. Days before the election, Obama gave an evasive response in a YouTube interview suggesting to his critics that any voter fraud committed by illegal aliens would not be prosecuted under his administration.

True The Vote, an organization dedicated to stopping voter fraud, strongly backed Trump’s claims about illegal voting.

“True the Vote absolutely supports President-elect Trump’s recent comment about the impact of illegal voting, as reflected in the national popular vote,” the group said in a statement. “We are still collecting data and will be for several months, but our intent is to publish a comprehensive study on the significant impact of illegal voting in all of its many forms and begin a national discussion on how voters, states, and the Trump Administration can best address this growing problem.”