Fire crews say they may have found a crack in the damaged industrial tank in California. It could change their entire strategy, as 50,000 residents remain evacuated. GARDEN GROVE, Calif. — Crews say they may have found a crack in the damaged industrial tank at an aerospace facility in Orange County, California. The tank, located at the GKN Aerospace facility in Garden Grove, contains thousands of gallons of methyl methacrylate, a highly flammable and toxic chemical used to make plastics. It overheated last week and began leaking vapors into the air, forcing 50,000 people to evacuate. Officials fear the tank…