SURFSIDE, Fla.—Rescuers searched through fresh rubble Monday after the last of the collapsed Florida condo building was demolished, which allowed crews into previously inaccessible places, including bedrooms where people were believed to be sleeping at the time of the disaster, officials said. But they faced a new challenge from thunderstorms that hit the area as Tropical Storm Elsa approached the state. Four more victims were discovered in the new pile, Miami-Dade Assistant Fire Chief Raide Jadallah told family members, raising the death toll to 28 people. Another 117 people remain unaccounted for. The demolition late Sunday was crucial to the search-and-rescue effort, officials said, and raised the prospect that crews could increase both the pace of their work and the number of searchers at the site, although the chance of finding survivors 12 days after the June 24 collapse has diminished. “We know that with every day that goes by, …