About 50 migrants boarded the boat during incidents at a pro-migrant march by some 2,000 people before police evacuated them in early evening.
British premier David Cameron calls President Hollande to ask for assurances that ferry dispute will not drag on through the summer.
Eurostar and Eurotunnel services resume but delays continue across Kent as ferry services to and from Dover cancelled due to blockade.
Up to 600 workers at MyFerryLink risk losing their jobs on July 2 following decision by Eurotunnel to end its partnership with the company.
SNCM, which links Corsica with mainland, has told staff it will put company in receivership, a move which could help it escape EU aid ruling.
Transport minister Frederic Cuvillier says ferry operator SNCM needs help to shield it from EU order to repay €440 million in state aid.