Parsons Green: What we know about the explosion and investigation so far

Armed police close to Parsons Green station in west London after the explosion on a packed London Underground train. PA
Armed police close to Parsons Green station in west London after the explosion on a packed London Underground train. PA

Detectives investigating an explosion on a London Underground train which sent passengers and those in the vicinity fleeing in fear have made their first arrest.

Here is what we know about the incident so far: