Federal law enforcement agencies have launched a criminal investigation into the use of American Express cards issued by the Republican Party of Florida to elected officials and staff, according to sources familiar with the inquiry. The IRS is also looking at the tax records of at least three former party credit card holders â€” former Florida House Speaker Marco Rubio, ex-state party chairman Jim Greer and ex-party executive director Delmar Johnson â€” to determine whether they misused their party credit cards for personal expenses, according to a source familiar with the preliminary inquiry. Rubio billed the party for more than $100,000 during the two years he served as House speaker, according to credit card statements obtained by the St. Petersburg Times and Miami Herald. The charges included repairs to the family minivan, grocery bills, plane tickets for his wife and purchases from retailers ranging from a wine store near his home to Apple's online store. Rubio also charged the party for dozens of meals during the annual lawmaking session in Tallahassee, even though he received taxpayer subsidies for his meals. Rubio acknowledged in February that he double-billed state taxpayers and the party for several plane flights from South Florida to Tallahassee. He said he would pay the party back about for eight flights totaling about $3,000, but the party said Tuesday it had not received a check. Harris said the campaign has determined that only six were double-billed and is waiting for the party to verify the exact amount. Rubio's tax attorney, Steve Wasserstein, said Tuesday that the double-billing was an "accounting mistake'' that does not require an amended filing and will be easily rectified when Rubio repays the party. U.S. attorney, IRS and FBI investigating Florida GOP credit card use - St. Petersburg Times How does one "accidentally" double-bill? Repeatedly?