California utilities have warned their customers that natural gas prices will be high this winter, but according to the federal government in a report released this week, prices started rising in the spring. Natural gas prices in June were the second-highest they have been this year in the state?with commercial users paying $7.79\/thousand cubic feet, down from $8.73 in March. Industrial users paid $7.04 for the same unit, down from $7.77, while the price for residential consumers was the same both months, $9.53, according to the Energy Information Administration. The first six months of this year, prices were still below those in 2001. The monthly 2001 prices fluctuated from a high of $12.35 for commercial users and $10.06 for the industrial category. The highest residential price was $13.92 for residential users. The figures punch holes in the belief that natural gas prices are escalating because demand is rising. ?The problem is on the supply side, not on the demand side,? said Rich Ferguson, researcher with the Center for Energy Efficiency and Renewable Technologies.