TOKYO — A strong earthquake late Saturday struck a mountainous area of central Japan that hosted the 1998 Winter Olympics, knocking down at least 10 homes in a resort town and injuring more than 20 people, officials said. The U.S. Geological Survey measured the quake’s magnitude at 6.2. Since the quake occurred inland, there was no possibility of a tsunami. About 15 people were treated for injuries at a public hospital in the city of Omachi, three of whom were seriously injured, officials told Japan’s Kyodo news agency. “We are trying to assess the situation as quickly as possible, and we’ll do our utmost for the rescue of the injured people,” said Japan’s top government spokesman, Yoshihide Suga. The National Police Agency told Japan’s Kyodo news agency that 21 people were trapped underneath the collapsed houses, but they all were rescued, with two of them injured.