WASHINGTON (AP) -- The Obama administration is tripling the number of workers processing Cash for Clunkers transactions as some dealers complain the government has been slow to reimburse them for the car incentives of up to $4,500 per vehicle. An administration official said Monday the Transportation Department hoped to have 1,100 public and private sector workers processing the vouchers by the end of the week, up from a work force of about 350 through the end of last week. Employees at a department service center in Oklahoma City have taken the lead in processing the vouchers, the official said, and workers have responded to calls for voluntary overtime to process the forms. The official was not authorized to discuss the work force issues publicly and spoke on the condition of anonymity. Dealers have reported submitting tens of thousands of dollars - in some cases more - worth of rebates to the federal government for repayment that are still outstanding. Many report they have been repaid for only a small fraction of the deals they made under the program, creating strain on cash flows at dealers nationwide. http://hosted.ap.org/dynamic/stories/U/US_CASH_FOR_CLUNKERS?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT