A fleet of Maryland State Police medical helicopters has been grounded until investigators determine the cause of a deadly weekend crash, officials say.State Sen. John C. Astle said all medical evacuation helicopters in Maryland are grounded while investigators attempt to find out if the fatal medevac crash was indicative of a major system flaw, The Baltimore Sun reported Monday.At this point, we don't know all the facts, we don't know the causal factors, and unless you're sitting in that aircraft next to the guy it's hard to know what he was going through, the Democratic state lawmaker said.Saturday's crash in Prince George's County, Md., claimed the lives of four people and left a sole survivor in critical-but-stable condition. ...