PARIS (AP) — A count by French maritime authorities shows that the number of migrants who attempted to cross the English Channel in small boats exploded last year, when more than 2,700 people were rescued at sea or stopped while trying to reach Britain from France.

Maritime officials said the 2019 figure is more than four times larger than the previous years’ count of cross-Channel migration. The French officials could not say whether the increase in attempts to reach Britain was linked to migrants fearing that Brexit might bring tighter borders.

It was not known how many migrants successfully made the crossing.

The passage, while a short distance, is fraught with risks, Last year brought four deaths, the first ones since migrants started using small vessels to go across the Channel in 2016, the maritime prefecture for the English Channel and North Sea region said Wednesday.

Small vessels can easily fail in the rough waters of the English Channel, known for high winds and strong currents. Nearly 25% of the world’s maritime traffic passes through the Channel from France to Britain, the Maritime Prefecture noted in its count.

The Twitter feed of the Maritime Prefecture showed 74 migrants rescued so far in 2020.

Migrants “are often badly equipped, in overloaded boats which aren’t made for this and are quickly going under,” into cold waters, spokeswoman Marine Monjarde said by telephone.

Migrants have long used northern France as a launching point to sneak into Britain, either through the Channel vehicle tunnel or on ferries. Both French and British customs agents and police are posted in the port of Calais.