Some North Korean officials returned to an inter-Korean liaison office on Monday, Seoul said. The Unification Ministry said that four to five North Korean officials showed up for work at the liaison office in the North Korean border town of Kaesong. Three days ago, Pyongyang abruptly withdrew its entire staff citing unspecified instructions from “higher-level authorities.” It wasn’t immediately clear why North Korea sent some workers back to the office or whether it would restore a full staff, AP said. The North’s decision to withdraw its staff on Friday came a week after its vice foreign minister threatened to pull out of nuclear negotiations with the US following the collapse of a nuclear summit last month between leader Kim Jong-un and President Donald Trump.