The 103 people, thought to be Romanian gypsies, were arrested on Thursday at Dartford International Ferry Terminal, after travelling by boat from the Belgian port of Zeebrugge.

Those held, whose number included children and babies, were due to be interviewed by immigration officers later on Friday, Kent Police said.

Inspector Dave Berry said the alarm was raised when the families were seen trying to leave the terminal site.

Officers spent more than two hours rounding up the suspects and transporting them to four police stations in west Kent.

Kent social services officers were also drafted in to help cope with the flood of suspects.

Largest-ever group

"This is certainly the largest number that I've heard of," said Inspector Berry. "We sometimes see about 15 at a time, I've never seen this number before.

"These cases are always a bit of a headache but it's now an immigration matter - we are just housing them for the time being."

Reports suggested that the immigrants may have been transported across the Channel in freight containers.