At least 20 passengers, including 16 women, were killed in a collision of two motor boats in Nga Wun river in Myanmar late on Friday, sources with the Myanmar Fire Service said.With about 60 passengers on board, a motor boat collided with another one loaded with stones near Pathein Taman creek in the southwestern Ayayawaddy region at 8.00 p.m, Xinhua news agency reported.About 30 passengers escaped the collision unharmed, the sources said. The accident was reportedly caused by failure of the lighthouse. A rescue operation by authorities and local people was underway.