SURFSIDE, Fla.—Demolition specialists bored holes for explosive charges Sunday as they prepared to bring down the precarious but still-standing portion of a collapsed South Florida condo building. The work has suspended the search-and-rescue mission, but officials said it would eventually open up new areas for rescue teams to explore. The decision to demolish the Surfside building came after concerns mounted that the damaged structure was at risk of falling, endangering the crews below and preventing them from operating in some areas. “Our top priority is that the building come down as soon as possible, no matter what time that occurs and as safely as possible,” Miami-Dade County Mayor Daniella Levine Cava told a news conference Sunday. “Bringing down this building in a controlled manner is critical to expanding the scope of our search-and-rescue effort.” Eighty percent of the drilling work was complete by Sunday morning, and the remaining structure could …