WASHINGTON - Two election watchdog organizations on Thursday urged the Justice Department and Federal Election Commission to investigate more than $12 million in campaign contributions that were mysteriously funneled through two little-known companies in Tennessee to a prominent tea party group. The origin of the money, the largest anonymous political donations in a campaign year filled with them, remains a secret.

The watchdog groups said that routing the $12 million through the Tennessee companies appeared to violate a U.S. law prohibiting the practice of laundering campaign contributions in the name of another person. They also said the lawyer in Tennessee who registered the companies, William S. Rose Jr. of Knoxville, may have violated three other laws by failing to organize each company as a political committee, register them as political committees, and file financial statements for them with the government.

Rose did not return a telephone message, text message, and e-mail from the Associated Press and could not otherwise be reached immediately for comment. He previously told AP that his business was a "family secret" and he was not obligated to disclose the origin of the $12 million routed through Specialty Investments Group Inc. and Kingston Pike Development Corp. Business records indicate that Rose registered Kingston Pike one day after he created Specialty Group, in the final weeks before Election Day.

The watchdog organizations, the Campaign Legal Center and Democracy 21, said a criminal investigation by the Justice Department was necessary "because the integrity of U.S. elections depends on the effective enforcement of the nation's campaign finance laws." They noted that, although the FEC traditionally enforces campaign finance laws and imposes civil fines for violations, the Justice Department can conduct criminal investigations of "knowing and willful" violations under the 1971 Federal Election Campaign Act.