The Associated Press reports that one year after a deadly oil-rig explosion set off the worst offshore spill in U.S. history, the environmental minefield of abandoned wells in the Gulf of Mexico is worse than first thought, with no quick solution in sight. A government list obtained by The Associated Press shows that in addition to 27,000 oil and gas wells that were sealed with cement and abandoned without any regular monitoring, another 3,200 old wells have quietly been left unused without any cement plugging to help prevent leaks. Without those plugs, there is little to prevent powerful leaks from pushing to the surface, so these wells could be an even greater environmental threat than wells that have been sealed and classified as either temporarily or permanently abandoned. The 3,200 unplugged wells are officially still active, but they haven''t been used for at least five years and there are no plans to restore production on them, according to the federal government. Operators have not been required to plug the wells because their leases have not expired.