Two men remain in police custody after counter-terror police officers searched six houses yesterday.
A property in Walthamstow was raided along with addresses in Greenford, Hounslow and High Wycombe by SO15 officers in the morning.
A number of vehicles were also searched as part of the investigation.
The men, aged 30 and 18 were arrested on suspicion of conspiracy to commit GBH from homes in Brentford and Hounslow.
Police say that the arrests were not related to terrorism.