Turn the underlined verbs from active into passive. Do not change the grammar tense. In your answer write the subject and the verb in the right form:

Example: The boys broke all windows in this house.
All windows were broken by the boys.

BREAKING NEWS!
This is Rachel Amber, Channel 5. We are on the air near the South Police Department where they 11) are keeping an unknown man. Here are the details!
Someone 12) had intruded into the City Art Gallery last night before they 12) switched on the alarm system. He 13) opened the back entrance door with a key when the night guards 13) were checking the front door video cameras. The night guards 14) noticed nothing at first. But later one of them 15) found the back door opened and 15) raised the alarm. The guards 16) searched all the building and 16) found a man in the staff room. They 17) called the police. Now the police representative 18) has just informed us that they 18) have arrested the man but they 18) cannot identify him. There is no file on him in the police database. The man keeps silence as if he is deaf and mute. Right now we 19) will show his photo. If someone recognizes him, please dial the number you see on the screen.