Seven private water wells in Jackson, Wis., have been contaminated with gasoline containing benzene from a broken pipe, government authorities said. Wisconsin\'s Department of Natural Resources announced Sunday gasoline containing benzene from a July 17 pipeline break continued to contaminate water supplies in Jackson, the Milwaukee Journal Sentinel reported. The gasoline leaks have increased the levels of benzene in the wells past the federal standards of 5 parts per billion. One of the earliest contaminated wells contained 2,730 parts per billion of benzene, 546 times greater than the federal standard. Benzene is known to cause cancer. Authorities are planning to install water treatment systems capable of removing gasoline in 11 private wells.