Some 23 migrants, including three children, have been detained in Kent after crossing the Channel in small boats.
Nine were found on a beach in Folkestone, six at Dover and eight rescued off the coast nearby.
French authorities also rescued 11 people, five of whom were suffering from hypothermia, from a small boat.
Lifeboat crews were sent from Dover and Littlestone-on-Sea to Sandgate, Folkestone, at 00:45 GMT.
Charlie Davies, operations manager of Littlestone-on-Sea RNLI, said it was called to reports of a "craft off the beach at Sandgate", but the boat had landed by the time they arrived.
"The people on the boat had got on the beach, but they were met by Border Force and Kent Police," he said.
He said the craft was a 4m (13ft) rigid-hulled inflatable boat with an outboard motor.
The boat's occupants - five men, one woman, two boys and a girl - were detained by Border Force officers.
The Home Office said Border Force officers were "deployed to attend on shore" in Folkestone and detained nine migrants, who are "being processed in line with the Immigration Rules".
Separately, the Border Force assisted with a small boat at Dover on Thursday, the Home Office said.
At about 08:45 an inflatable boat carrying eight adult male Iranian migrants was spotted.
All were brought to shore for medical assessment and transferred to immigration officials for interview.
Six Iranian migrants were earlier detained on Shakespeare Beach in Dover at about 08:30.
French authorities said several passenger ships reported a small boat in French waters off the coast of Calais between 22:40 GMT and 23:40 GMT.
Eleven adults, five of whom were suffering from hypothermia, were rescued by the gendarmerie maritime at 00:45 GMT. They were taken to Boulogne.