The federal Justice Department handed out nearly $100 million in grant money to the host cities for the 2012 Democratic and Republican national conventions -- but not all of it was used correctly, two new audits show.

Charlotte and Tampa each received roughly $50 million each to help with security for the DNC and RNC, respectively. However, the Justice Department's inspector general found spending issues with vehicle purchases and overtime pay in both cities, and Tampa had to return more than $900,000 to the federal government.

Auditors spotted a truck purchased in the mayor of Tampa's reserved parking spot — a truck that was bought using funds earmarked only for "criminal justice purposes," according to the audit. The mayor was also seen getting in and out of the vehicle.

From Tampa's WTSP-TV:

A spokesperson for Mayor Bob Buckhorn deferred questions to a Tampa Police Department spokesperson, who said the vehicle was designated for "dignitary protection," including the mayor. And even though Buckhorn sometimes drives the vehicle himself, TPD considers his around-the-clock protection a "criminal justice purpose," and will clarify its interdepartmental procedures to eliminate any DOJ concerns.

The auditors also questioned $25,000 worth of overtime, salary or fringe benefits costs paid to security personnel, such as firemen.

In Charlotte, site of the Democratic convention, the IG found the city modified two SUVs worth $54,000. Though Charlotte said the modifications were necessary under Justice Department guidelines, they were not, according to the audit.

The city of Charlotte was also reimbursed for $79,000 in unallowable costs, including salaries, overtime and retirement payments to various security personnel.

Both audits concluded the cities "generally claimed costs in accordance with grant requirements," but also said that fixing the problems would ensure further cities hosting conventions spend their grant money the right way.

Charlotte was invited by the RNC to bid on hosting the 2016 convention earlier this year, but city officials announced in late January they were declining the offer, the Charlotte Observer reported. The convention ginned up $164 million in economic impact for the region, but private fundraising to put on the event fell short. The city borrowed $10 million from local power provider Duke Energy to cover the costs, and $6 million of that will not be paid back; the company's shareholders will have to eat the cost, the newspaper said.

The Tampa RNC host committee has since estimated that convention had an economic impact of more than $400 million in the Tampa Bay area.

View the RNC audit here and the DNC audit here.