Video footage has caught the moment armed police raided a Manchester house believed to be connected to Salman Abedi - the suspected suicide bomber in the Ariana Grande concert attack.
A photo of an investigator walking out of the property shows the person holding a book titled Know Your Chemicals.
The clue appears to provide a strong connection to Abedi's alleged act of taking taking a home-made explosive device to the Manchester Arena.
The Guardian reported that police have obtained CCTV footage showing Abedi entering the arena, where he is believed to have detonated a device in a backpack, in the arena's foyer.
The red brick house is in the south of the city. Abedi was 22 years old and born in Manchester to parents of Libyan origin.
Police are working to find out if Abedi was working alone or in a network.