Sens. Dianne Feinstein of California, Claire McCaskill of Missouri, Jon Tester of Montana, Bill Nelson of Florida and Charles Schumer of New York say the colleges are fronts for people who pay to illegally enter the United States.

The Democrats are calling on the U.S. Citizenship and Immigration Services and Homeland Security to share information that could help identify the fake colleges.

The senators note several of the Sept. 11 terrorists entered the United States on student visas. They also cite recent incidents in California and in Florida where schools have been accused of being involved in the illegal visa scheme.

"Sham universities are not real institutions of higher learning, but rather operate solely for the purpose of manipulating immigration law to admit foreign nationals into the country," the senators stated in the letter released Sunday. "When the student visa program can be manipulated by bad actors, it threatens the viability of the entire program for the large majority of bona fide participants."

The senators will ask the federal departments to determine "high-risk factors" within 90 days and conduct site visits at schools that show a high risk factor through data — or the lack of data — that legitimate schools must provide to the federal government. The senators also seek stiffer penalties for "sham universities" that engage in student visa fraud.

"The existing penalties for student visa fraud are simply too low to deter bad actors who can reap large rewards by operating for-profit sham universities and charging foreigners thousands of dollars to come to the United States," the senators wrote. "These new penalties will assist you in obtaining justice for the bad actors who compromise the system."

There was no immediate comment from the federal departments.