LONDON — Britain’s Border Force intercepted 74 people Saturday, including minors, on eight vessels trying to cross the English Channel into Britain. French authorities stopped two other boats.

The interceptions on a warm sunny day will heighten concerns that improving weather will encourage smugglers to try their luck at bringing more migrants to the U.K. from France.

Authorities said a criminal investigation was underway. The nationalities of the migrants were still being determined. Coastguard officials said the incidents stretched along Britain’s southeast coast, from the port of Dover to Winchelsea Beach near Hastings, 50 miles away.

Home Secretary Sajid Javid vowed he would work with French border authorities to halt this rise in human trafficking across the Channel.

“Those who choose to make this dangerous journey across one of the busiest shipping lanes in the world are putting their lives in grave danger — and I will continue to do all I can to stop them,” he said in a statement Saturday night.

Local lawmaker Charlie Elphicke suggested the numbers were unprecedented and demanded action.

“This crisis was meant to have been dealt with at Christmas, yet numbers continue to rise,” he wrote on Twitter. “The Home Office needs to get a grip on this crisis.”

The reports about migrants using small boats to cross the English Channel to Britain are politically explosive, even though Britain has seen nowhere near the number of migrant sea crossings that have hit fellow European Union nations Spain, Italy and Greece. So far this year, over 21,300 migrants have crossed the Mediterranean Sea into Europe, and at least 519 others have died trying, according to the International Organization for Migration.

In December last year, Javid declared a rise in migrant crossings to be a “major incident.” He said Saturday that since then, two cutters have returned to U.K. waters from overseas and he has agreed upon a joint action plan to halt people smuggling with his French counterparts.

Officials have blamed the influx on smuggling gangs.

“It is an established principle that those in need of protection should claim asylum in the first safe country they reach, and since January, more than 30 people who arrived illegally in the U.K. in small boats have been returned to Europe,” Javid said. “We will continue to seek to return anyone who has entered the U.K. illegally.”

Overall, migration into Europe is down substantially since over 1 million asylum-seekers and migrants came to the continent in 2015, but the issue still resonates politically, including in the elections last week to the European Parliament.