The authorities are investigating the explosion , he said . NEW : Official says water , gas and sulfur trioxide may have caused the explosion . The cause of the blast is unlikely to have been a bomb , a police official says . A witness reports hearing a ' very big , loud noise of explosion ' before fleeing . The explosion occurred in a residential area of Yangon .
NEW : Official says water , gas and sulfur trioxide may have caused the explosion . The cause of the blast is unlikely to have been a bomb , a police official says . A witness reports hearing a ' very big , loud noise of explosion ' before fleeing . The explosion occurred in a residential area of Yangon .