The arrest of two Iraq-born refugees on terror-related charges has recharged Capitol Hill calls for the Obama administration to pull back on plans to welcome thousands more refugees from Middle East warzones.

“It is disturbing, though not surprising, that terrorists have succeeded in exploiting our refugee system to come to the U.S. and aid ISIS,” Rep. Lamar Smith, R-Texas, said Friday.

Officials announced the arrests on Thursday, in California and Texas; it’s unclear if they’re related.

One of the criminal complaints accused 23-year-old Aws Mohammed Younis Al-Jayab, of Sacramento, Calif., of traveling to Syria to fight alongside terrorist organizations and lying to government investigators about it. He originally came to the U.S. from Syria in 2012. Investigators said he discussed plans to return, and wrote that he was "eager to see blood."

Almost simultaneously in Houston, authorities announced the arrest of Omar Faraj Saeed Al Hardan, 24, on charges of attempting to provide material support to ISIS.

Republicans, in Washington and on the campaign trail, seized on the arrests to renew their push for immediate security changes to minimize the risk of ISIS and other fighters exploiting the expanded refugee program.

“While I commend the FBI for their hard work, these arrests heighten my concern that our refugee program is susceptible to exploitation by terrorists,” House Homeland Security Committee Chairman Michael McCaul, R-Texas, said in a statement. He touted House-passed legislation that would require top security officials to certify to Congress that every refugee accepted is not a security threat.

Smith proposed going further, and temporarily halting “all admission and resettlement of refugees until we can verify that every single ‘gap’ in our security screening has been addressed.”

Smith also is pushing legislation to protect states that refuse to participate in the resettlement program, and to halt the resettlement entirely until the administration submits reports on safety and costs to Congress.

On the campaign trail, Texas Sen. Ted Cruz was quick to cite the arrests in calling for changes.

Speaking in Iowa, he called for a retroactive review of all refugees who have come to the United States from what he calls "high-risk countries."

“We need to systematically examine the national security threats,” the Republican presidential candidate said.

White House Press Secretary Josh Earnest, while saying he could not discuss the specifics of the two latest terror-related cases, on Friday defended the refugee program as secure.

“No one’s allowed to short-circuit this system,” Earnest said, adding that refugees are subject to the “most rigorous screening” of anyone entering the U.S. He said this includes a “careful review of biographic and biometric information,” in-person interviews and other steps.

The Paris and San Bernardino terror attacks last year already had complicated the administration’s plans to take in more refugees, particularly from Syria.

Obama wants to accept at least 10,000 Syrian refugees into the U.S. in 2016 – the decision followed mounting international pressure for the U.S. to do more to shoulder the burden of the refugee crisis that has spilled into countries like Lebanon and Jordan, and nations across Europe. Heart-breaking images of children and families struggling to flee the violence in Syria fueled those calls – but U.S. lawmakers on both sides of the aisle have voiced concerns about whether the government can properly vet applicants, particularly from war-torn Syria where effective background checks are difficult to conduct.

Officials at the state level also have tried to fight back against the administration’s plans, and revived their concerns after the two latest arrests.

"This is precisely why I called for a halt to refugees entering the U.S. from countries substantially controlled by terrorists," Texas Gov. Greg Abbott said. "I once again urge the President to halt the resettlement of these refugees in the United States until there is an effective vetting process that will ensure refugees do not compromise the safety of Americans and Texans."

According to the complaint, Al-Jayab traveled to Syria from Chicago via Turkey in November 2013. He remained in Syria until the following January and fought alongside several terror groups, including Ansar al-Islam, which merged with ISIS in 2014 after Al-Jayab had returned to the United States. He settled in Sacramento following his return to the U.S.

U.S. Attorney Benjamin Wagner said in a statement that while Al-Jayab posed a potential safety threat, “there is no indication that he planned any acts of terrorism in this country.”

In the Texas case, the indictment of Hardan states that beginning in May 2014, Hardan "did unlawfully and knowingly attempt to provide material support and resources ... training, expert advice and assistance, to a foreign terrorist organization, namely the Islamic State of Iraq."

The indictment claims that Hardan, who arrived in the U.S. in 2009 and became a legal permanent resident in 2011, concealed his association with ISIS on his citizenship application in August 2014 and lied about receiving machine gun training when he was interviewed by Immigration and Customs Enforcement agents.

The Associated Press contributed to this report.