18:00Six O'Clock News10/03/2018 Nerve agent attack: 240 witnesses identifiedBBC Radio 4 Duration: 15 minutes Sat 10th Mar 2018, 18:00 on BBC Radio 4 FMAvailable for over a yearListen nowThe investigation into the attack on a former Russian spy involves 250 officers.GenresNewsFormatsBulletinsBrandSix O'Clock News Source: BBC Online