The posted list of felony charges against Mohamed Sabry Soliman, 45, also includes charges of murder in the first degree, although police have said on social media that no victims were killed in the attack, which took place on Sunday in the city of Boulder.
Authorities could not be reached immediately to clarify.
The suspect is being held on $US10 million ($A15 million) bail.
Few details were available about the suspect but Todd Lyons, acting director of US Immigration and Customs Enforcement, said Soliman had overstayed a visa and had an expired work permit.
"There are millions of individuals like this that we are attempting to locate from the past administration that weren't properly screened that were allowed in," Lyons said during a press conference in Boston.
"I will tell you that's a huge effort for ICE right now."
Under former president Joe Biden, ICE prioritised arrests of serious criminals and called for officers to consider humanitarian factors when making arrests.
The attack was the latest act of violence aimed at Jewish people in the US linked to outrage over Israel's escalating military offensive in the Gaza Strip.
It followed the fatal shooting of two Israel embassy aides that took place outside Washington DC's Capital Jewish Museum last month.
Lyons declined to provide more information but a Department of Homeland Security spokesperson previously said Soliman had entered the country in August 2022 and filed for asylum the following month.
"The suspect, Mohamed Soliman, is illegally in our country," the spokesperson said.
Soliman is scheduled for a court hearing later on Monday.
US President Donald Trump said in a social media post that such attacks would not be tolerated.
"This is yet another example of why we must keep our Borders SECURE, and deport Illegal, Anti-American Radicals from our Homeland," he said.
Witnesses reported the suspect used a makeshift flamethrower and threw an incendiary device into the crowd.
He was heard to yell "Free Palestine," according to the FBI, during what the agency called a "targeted terror attack".
Four women and four men between 52 and 88 years of age were transported to hospitals after the attack, Boulder Police said.
The attack took place on the Pearl Street Mall, a popular pedestrian shopping district near the University of Colorado, during an event organised by Run for Their Lives, an organisation devoted to drawing attention to the hostages seized in the aftermath of Hamas' 2023 attack on Israel.
Rabbi Yisroel Wilhelm, the Chabad director at the University of Colorado, Boulder, told CBS Colorado that the 88-year-old victim was a Holocaust refugee who fled Europe.
The FBI raided and searched Soliman's home in El Paso County, Colorado, the agency said on social media.
"As this is an ongoing investigation, no additional information is available at this time."
