Change into the passive.
A thief stole an important painting from the National Gallery yesterday. The gallery's security guard reported the robbery to the police at 7pm last night. The police have arrested a man who they are questioning at the moment. The police think he is the man resposible but they haven't found any proof as yet. The police gave no more information. They said they will carry out a full investigation. Galllery staff said the gallery will not open to the public this week.