yesterday. those are all areas we ll be watching as these storms continue to move right on down the corridor. we ll continue to keep you posted. and again, severe thunderstorm warnings in effect for washington and frederick county. we ll continue to keep you posted. the other big story tonight, tragedy in western maryland. four people were killed when a helicopter crashed near a highway and exploded into flames. tonight, the focus is on finding a cause. eyewitness news has been following this story since it first broke. alex demetrick is live with the latest. reporter: well, denise, this helicopter was flying under visual flight rules, not instruments. and not being able to see what was up ahead may have caused this crash. reporter: the helicopter went down in the median of the eastbound lanes of i-70, about 10:30 last night, along a stretch of south mountain, near smith burg. all four people were killed either in the crash or the fire that followed. there had been stor