"At this point, this is still under investigation by the FBI to determine any ties or affiliations these individuals may have had with ISIL or organizations around the world," White House Press Secretary Josh Earnest said. "The thing that we can say definitively, because of the quick, professional, brave work of local law enforcement forces, is an attempted terrorist act was foiled."
The shooting attack in Garland, Texas came during a contest where participants drew cartoons of Mohammed. Images of Mohammed are considered highly offensive in Islam.
Two gunmen injured a security guard before being shot dead by police.
ISIS later claimed responsibility for the attack in a broadcast on its radio state.
While Earnest said on Tuesday that U.S. intelligence services couldn't yet determine the extent to which the Texas gunmen were tied to ISIS, he acknowledged the group's attempts to reach young extremists outside Iraq and Syria.
"There are extremists around the globe, including those affiliated with ISIL, who are trying to capitalize on the opportunity presented by social media, to try to communicate with individuals around the world, including in the United States," Earnest said.
Also on Tuesday, Sen. Richard Burr, the chairman of the Senate Intelligence Committee, said there was no "definitive thread yet" tying the attack to the terror group. But Burr, who has been pushing for an extension of the portions of the Patriot Act that are due to expire at the end of the month, said the incident "reinforces the need" to continue anti-terror programs.
Meanwhile, Sen. Lindsey Graham, R-South Carolina, a potential 2016 presidential candidate, and Texas Republican Sen. John Cornyn said they weren't sure if ISIS was behind the attack or whether the group was merely taking credit after Sunday's incident.