WASHINGTON, July 6 (UPI) -- A wave of gasoline siphoning in Washington has prompted police to issue warnings, advising people to report such theft even it seems like a nuisance.

Steep increases in gasoline prices have led to siphoning in many parts of the country. Average prices of more than $4 a gallon for unleaded and $5 for diesel fuel have made siphoning easy and profitable, The Washington Post (NYSE:WPO) reported.

Gas tank filler caps outfitted with locks are selling well.

Marco Santiago, a D.C. police community relations coordinator, told the Post police are urging people to report gasoline theft. Melanie Hadley, a spokeswoman for the Montgomery County, Md., police, said the department had received seven reports of gasoline theft this year, after receiving none in 2007 -- but she said many people don't bother calling police over a few gallons of gas.

"If people don't report it, then we don't know it's occurring and we can't address it," Hadley said.

Prince William County, Va., police recently charged a man with grand larceny for allegedly stealing more than $50,000 worth of gas from a station during a period of months. Phillip Harris, 23, allegedly used an electronic device to turn on the pumps after hours,and then sold it to friends for half-price, the newspaper said.