Satellite images have revealed that North Korea has started rebuilding work on a facility previously used to test long-range missile engines, according to analysts. Two monitoring groups, the Center for Strategic Studies and 38 North, each say they observed activity at the Tongchang-ri satellite launch facility, which has been dormant since August. The work appears to have begun between Feb. 16 and March 2, meaning it could have happened shortly before, during, or immediately after Kim Jong Un and Donald Trump abruptly ended their second summit in Hanoi with no further agreement on denuclearization. Meanwhile, National Security Adviser John Bolton has warned North Korea it could be hit with even tougher sanctions if it doesn’t completely give up its nuclear-weapons program. “If they’re not willing to do it, President Trump has been very clear they’re not getting relief from the crushing economic sanctions that have been imposed on them,” Bolton told the Fox Business Network on Tuesday evening.