DETROIT --- Hybrid vehicle sales in the U.S. were up 49 percent during the first seven months of 2007, with the Midwest accounting for the biggest increase in sales. R.L. Polk & Co. reported that Oklahoma saw a 143-percent increase in hybrid vehicle registrations compared to the same period in 2006. Hawaii was the only state that saw a decrease in hybrid vehicle registrations. "The data indicates that hybrids have not hit a plateau and that there is room for continued growth within the marketplace in all regions," said Lonnie Miller, director of industry analysis for R.L. Polk. From January to July 2007, hybrid sales in the Midwest rose 57 percent --- higher than any other region. In that region, the most popular models were the Toyota Prius and the hybrid version of the Toyota Camry. During the same seven months in the West, hybrid sales rose 52 percent. In the Northeast, they climbed 49 percent. The South saw hybrid sales rise 42 percent.