PARIS — At least three migrants died early Sunday while attempting to cross the English Channel to Britain from northern France, authorities said. The deaths were confirmed after an early morning rescue operation involving French emergency services and the navy’s “Dauphin” helicopter.

Around 50 people were stranded in the water and on the beach near Sangatte at around 6 a.m., according to the regional prefecture. Rescuers assisted 45 individuals, including four who were transported to hospitals.

Three unconscious people were pulled from the water but could not be revived, despite efforts by medical teams. Prosecutors in Boulogne-sur-Mer opened an investigation.

Jacques Billant, the prefect of Pas-de-Calais, said an overcrowded boat may have contributed to the tragedy. “There were more people attempting to board than the boat could hold,” he said during a news conference Sunday.

Angela Eagle, the U.K. border security and asylum minister, said the boats were operated by smugglers the government has vowed to stop.

— The Associated Press