Four people have been arrested by police on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism in Syria
Two men aged 29 and 18 both from Levenshulme, and a 21-year-old woman from Trafford are in custody, Greater Manchester Police said.
A 29-year-old man from Oxford has been arrested by the South East Counter Terrorism Unit on suspicion of the same offence.
Police said a number of properties were now being searched as part of the investigation.
More top news
The 17-year-old was trapped for 30 hours in Australian shrubland but there was no report of a road accident to help the search.
The expansion of the probe came as Jeremy Corbyn declared Carillion's demise a "watershed moment" that should end "rip-off privatisation".
Cold with clear skies coupled with rain, sleet & snow