The police northeast counterterrorism unit confirmed they were probing a number of'offensive messages on social media and extreme social media content '.

Scotland Yard's counterterrorism unit has taken over the investigation.

They were held by officers from the West Midlands counterterrorism unit.

The plot was thwarted because police from the northwest counterterrorism unit arrested the youth on suspicion of threats to kill his teachers.

The airline is understood to have tipped off the counterterrorism unit.