On April 20, 2010, an explosion of high pressure methane gas sank British Petroleum (BP)'s Deepwater Horizon drilling rig, causing a leak that became one of the largest oil spills in history. The leak continued until the well was officially sealed on September 21, 2010 and released an estimated 560-585 tons of crude oil into the Gulf of Mexico. Following the spill, a massive clean-up effort was undertaken in an attempt to remedy the spill's effects. Health concerns for residents of the Gulf region remain due to contamination from the oil. Litigation relating to the spill has been extensive due to the impact on economic activity and the regional ecosystem. BP has set aside nearly $50 billion dollars for both litigation and settlements. While most private lawsuits were settled by 2012, the company continues to appeal decisions relating to the spill.