Five men and one woman in their 20s were detained yesterday morning in the departure zone of the Kent port, West Midlands police said on Twitter.
The arrests were part of an on-going investigation, and the suspects are not a family group and were not accompanied by children, police said.
Four of the men arrested are from Birmingham and in their 20s while a 26-year-old man and a 23-year-old woman of no fixed address were also held later. The suspects are being questioned at a police station in the West Midlands area, police said.
The arrests were made a day after 9 British nationals, including women and children, were detained in Turkey after allegedly trying to enter strife torn Syria amid fears the 'family' may have travelled there to join the dreaded Islamic State (IS) militant group.
One of them detained in Turkey for allegedly trying to cross illegally into Syria has been named as the son of a local Labour councillor from Rochdale in northern England.
Rochdale councillor Shakil Ahmed said he had thought his son Waheed, 22, was on a work placement in Birmingham.