TOKYO, May 23 (AFP) - A fire swept through a small mah-jong parlour on Sunday beside a highway in Yokohama, south of Tokyo, killing six men and injuring two others, police said. A fleet of 15 fire trucks needed half an hour to put out the blaze which destroyed the parlour housed on the first floor of a two-story building, police said. The sound of an explosion was heard before the fire started in late afternoon, police said.  