Libyan authorities have limited access to the flooded coastal city of Derna to dig through the mud and hollowed-out buildings for the more than 10,000 people still missing and presumed dead following a disaster that has already claimed more than 11,000 lives. Authorities warned Friday that waterborne disease and explosive ordnance that shifted during the early Monday flood could claim yet more lives. In the worst-affected areas of Derna, efforts to recover the dead and distribute aid have been plagued by confusion and a lack of resources. Libya’s two opposing governments, long divided by...