The watchdog group American Oversight sued the Department of Homeland Security on Wednesday, asserting the agency failed to provide records backing Secretary Markwayne Mullin's claim that 250,000 noncitizens registered to vote across four states.

American Oversight filed Freedom of Information Act requests seeking documentation for Mullin's figures. The group specifically requested records related to 190,832 alleged noncitizens registered in California, 35,152 in New Jersey, 15,903 in Nevada and 14,576 in Pennsylvania.

Mullin first presented these claims in a July speech, which followed President Trump's primetime remarks alleging past Chinese interference in U.S. elections.

Chioma Chukwu, executive director of American Oversight, said Mullin's office uses unsupported allegations of fraud to pressure election officials and undermine public confidence in election results.

Letters sent to the four states reveal discrepancies between the numbers DHS publicized and those communicated to state officials. The federal government's preliminary review found 118,000 names and other information matched in its files—less than half of Mullin's public estimate.

State officials questioned how Mullin could make such claims without access to state voter rolls, which contain personal information like Social Security numbers.

California Secretary of State Shirley Weber wrote to Mullin this summer: "I have serious doubts about the reliability of your data and accuracy of your claims, since my office has not shared our statewide voter registration list with DHS or any other federal agency or official."

Chukwu said if DHS possesses evidence to support its claims, it should release the information. She noted Mullin's claims have already unraveled in at least one state.