At least five migrants died in an attempt to cross the English Channel from an area near the French town of Wimereux on Tuesday, police said.
The French coast guard confirmed a police rescue operation had found several "lifeless bodies" following a failed attempt to cross the Channel.
A coast guard spokesperson said its agents were still operating at sea after what the official called a "busy" morning, with several crossing attempts.
The attempts took place after Britain's upper house of parliament passed legislation on Monday night that will allow the U.K. government to send asylum-seekers to Rwanda rather than stay in Britain for processing.
Stopping the flow of migrants is a priority for British Prime Minister Rishi Sunak's government, which says the Rwanda plan will act as a deterrent. Human rights groups and other critics say it is inhumane.
La Voix du Nord newpaper said about 100 migrants had been rescued early on Tuesday, with three helicopters and several rescue boats taking part in the operation.
Tens of thousands of migrants - many fleeing wars and poverty in Africa, the Middle East and Asia - have reached Britain in recent years by crossing the Channel in small boats on risky journeys organised by people-smuggling gangs.
The Channel is one of the world's busiest shipping lanes and currents are strong, making the crossing on small boats dangerous.
The people smugglers typically overload the boats, leaving them barely afloat and at risk of being lashed by the waves as they try to reach British shores.
