A letter, signed "Concerned Citizens of the United States," accompanied the list and reads, in part, that the writer "observes these individuals in our neighborhoods, driving on our streets, working in our stores, attending our schools and entering our public welfare buildings."
Two anti-immigration groups, the Minutemen and the Utah Coalition on Illegal Immigration, have said they're not responsible for the list.
"There is absolutely no justification for anyone ... releasing private information to the public," the Coalition's Ron Mortensen told the Salt Lake Tribune. "If someone has done that and they're in violation of any state laws they ought to be held accountable."
A co-chair of the Minutemen, Eli Cawley, told the Tribune he disapproved of the list. But he also told a local radio station, "If you had a legitimate list that didn't unnecessarily or negligently point out citizens and legal residents, then I think that would serve the greater interest."
One immigration advocate, Tony Yapias, says he suspects a government employee sent out the list.
The governor has ordered the state office of information technology to investigate. Other offices, including the Health Department and Workforce Services, are also seeing whether the information could have come from their offices.
It's not clear whether the people named on the list are actually undocumented. One woman on the list, reached by local TV station KSL, said she's been a legal resident for years and is due to get her citizenship next month. Another person on the list, however, admitted to being in the country illegally.
Utah is considering an anti-immigration law similar to Arizona's.