Complex sentence: On August 9,2011, the McCarthy Cottage and the E.T. Curtis Cottage next to the Little White House were destroyed in a fire which investigators believed had been started by lightning and thunderstorms that were in the area at the time.
Split into simpler sentences: On August 9,2011, the McCarthy Cottage and the E.T. Curtis Cottage next to the Little White House were destroyed in a fire. The cause is being investigated, but suspicion is being focused on lightning and thunderstorms that were in the area at the time.