When congressional Republicans were trying to halt the Syrian refugee program last fall, a central pillar of the Obama administration’s defense was that there was no more arduous way to enter the United States and that few if any refugees had ever been arrested on terrorism charges.

That argument took a big hit on Thursday night, when federal prosecutors unsealed indictments against two refugees from Iraq on charges involving international terrorism. Aws Mohammed Younis Al-Jayab, a 23-year-old Iraqi-born Palestinian living in California, allegedly flew to Syria in 2013 and 2014 to join terrorist groups and then lied to immigration officials questioning him about his activities upon his return. Al-Jayab arrived in the U.S. from Iraq in 2012 and also lived in Arizona and Wisconsin. He was charged with making false statements.

In a separate case, Omar Faraj Saeed Al Hardan, another Palestinian born in Iraq, was indicted on charges alleging that he provided material support to the Islamic State and then lied about it. Al Hardan, 24, was living in Houston and came to the U.S. as a refugee in 2009 before gaining permanent legal status two years later.

The arrests could revive the push by Republicans in Congress to suspend the refugee program for Syria and Iraq, which stalled at the end of last year. Senior lawmakers and presidential candidates rushed to publicize the arrests to bolster their insistence that despite nearly two-year waits for most refugees, the program was not secure enough.

“If this is not enough evidence, I don’t know what is,” Representative Michael McCaul of Texas said at a Capitol press conference. As chairman of the Homeland Security Committee, McCaul authored legislation that the House passed in November with a veto-proof majority. McCaul and other House Republicans called on the Senate to take up the bill. Majority Leader Mitch McConnell has said it’ll be considered early in 2016.

“They’re ticking time bombs, and how many ticking time bombs are we going to bring in through these refugee programs before we have a proper vetting process in place?” McCaul said. “If these two guys got through the cracks, how many more are in there?” McCaul said he had been briefed on the FBI’s investigation and that while he couldn’t talk about it until Thursday’s charges were announced, it clearly fed into the urgency that Republicans felt when they pushed the refugee bill so quickly through the House, with barely any time for debate.

Obama administration officials have said refugees from Syria already go through the most intense scrutiny of any entrants into the U.S., and the White House has said suspending the program would send a terrible signal given the nation’s history as an asylum nation. The government plans to resettle 10,000 additional refugees this year, a much lower total than Canada or many European nations plan to accept. Josh Earnest, the White House press secretary, wouldn’t comment on the arrests during his briefing on Friday but touted the strength of the screening process.

Citing testimony by FBI director James Comey, Republicans have said that because of the chaos caused by the civil war and ISIS’s foothold in Syria, there isn’t enough intelligence to determine whether potential refugees present a security risk. McCaul said that based on the briefings he’s received, he didn’t know if either of the two men arrested were radicalized before or after they arrived in the U.S.

Critics of the refugee program have accused the administration of overstating their success in keeping terrorists from infiltrating the U.S. They point to reporting from ABC News that a pair of Iraqi refugees who were resettled in Bowling Green, Kentucky, were later found to have links to al Qaeda.

On the presidential campaign trail, Ted Cruz pounced on the arrests within an hour or so of the announced indictment. He called a press conference in Iowa on Thursday evening to demand that U.S. officials retroactively evaluate refugees that have already been resettled from the Middle East in light of the indictment. "These arrests underscore the need... for President Obama to suspend this indefensible policy putting political correctness ahead of national security,” Cruz said, according to CNN.

The push to pause the refugee program faded in December as both parties turned their attention to tightening the visa-waiver-travel program, which the administration said was a bigger risk for exploitation. Changes to that policy were included in the year-end omnibus spending bill, while the House’s bill suspending the Syrian refugee program was not. With the Senate expected to take up that measure soon, the refugee arrests on Thursday may have given the issue new life.