Around 2,500 migrants, mostly from Sudan, Eritrea and Syria, live in a makeshift tent village in Calais known as "the jungle" and they regularly make attempts to cross the Channel.
Last year there were 30,000 recorded attempts, mainly by refugees attempting to conceal themselves in trucks.
They took advantage of slow-moving traffic caught in a protest organised by sailors from the French ferry company MyFerryLink, angry over plans by Eurotunnel to sell two of their ferries to rival Danish firm DFDS.
Unions say they fear as many as 120 jobs could be at risk from the potential sale.
Cars and trucks were banked up for several hours on Tuesday and the train services were suspended until the evening.
The demonstrators occupied the docks in Calais port, preventing passengers from disembarking and forcing ferries to be diverted to the nearby port of Dunkirk.
Police also used tear gas to disperse some 200 MyFerryLink workers who had forced their way onto the tracks and burnt tyres.
Cross-Channel Eurostar train services resumed on Wednesday after repairs to the track were completed.
Alarmed by the unrest, the French government issued a statement late Tuesday calling on Eurotunnel to "reexamine its plan" and to "work towards a better solution with regards to employment".