News at Seven-Thirty: cleaning efforts have been stepped up at Sheraton Hotel; principal officials took part in the "Clean Hong Kong Day" activities; Costa Rica has reported its first H1N1 flu fatality case; a gas pipeline exploded in Moscow; Mandatory evacuation order in California has lifted; authorities decided to rebuild Beichuan from scratch at a new location; teachers at private swimming classes are not required to hold any qualification; a charity organisation treated some elderly people to a Thai buffet on the Mother’s Day; Obama became the comedian-in-chief.