CLEAN : UK police say no guarantees of no further contaminations

The transcript discusses the progress of an investigation into how Dawn and Charlie came into contact with a nerve agent. A murder investigation was launched following the death of Dawn Sturgess. Public health officials assure that the risk to the public is low but advise against picking up strange items. Despite concerns from 21 individuals, all have been screened and cleared.

What is the main line of inquiry in the investigation mentioned?

What tragic event is the investigation centered around?

What type of agent was involved in the incident?

What was emphasized about the risk to the general public?

What advice was given to the public regarding strange items?