BNSF spokesman Gus Melonas says the slide came off a 100-foot slope and struck the train at about 1:30 p.m. Monday, in the same area where a slide covered the tracks earlier in the day. Seven cars were derailed.
Witness Ricky Ivelia saw the whole thing unfold.
"I saw the hill start to go. It went down and hit the first car and it tipped over, then more cars kept tipping over. It was crazy how loud it was and how slow it all happened," he said.
The cars were carrying various types of freight, including small packages of disinfectant and chemicals used in cleaning supplies and fertilizer.
Melonas says a hazardous materials team did respond, but there is no threat to the environment or public health.
The tracks are expected to remain closed for freight trains at least until tomorrow, and Amtrak and Sound Transit Sounder passenger trains must observe a 48-hour safety moratorium before then can resume travel.