French coastguards rescued 157 people from a boat carrying migrants that caught fire in the English Channel on Tuesday near the port of Boulogne-sur-Mer, the local administration said in a statement.

Three coastguard ships rescued those on board, the local French administration which handles the English Channel and North Sea areas said.

Migration has been one of Europe’s most divisive political issues since a crisis in 2015-16, when more than a million refugees and migrants — many of them fleeing war in Syria — arrived in Europe.

Last week three people died while trying to cross the Channel on a small boat.

Tuesday’s rescue highlights the growing dangers of Channel crossings as human traffickers cram ever larger numbers of migrants onto flimsy boats. British Prime Minister Andy Burnham pledged on Sunday to be “relentless” in curbing small-boat arrivals.

The Channel is one of the world’s busiest shipping lanes, and its strong currents have resulted in the deaths of many migrants trying to cross over from France to Britain. Human traffickers typically overload their dinghies, leaving them barely afloat.

“This incident underlines the terrible dangers of small boat crossings. We continue to work relentlessly with the French and our partners overseas to prevent these perilous journeys,” a British government spokesperson said.

On Monday, Britain’s right-wing Reform UK party said that if elected, it would stop asylum seekers with what it said would be the largest military operation in the Channel since World War Two.