Children were among a group of migrants detained by Border Force off the coast of Dover on Tuesday.
A group of “up to 38” people were caught travelling across the Channel to Kent shortly before midday, a witness said.
A spokesman for the Home Office said Border Force was “dealing with three ongoing small boat incidents off the Kent and Sussex coasts” into the afternoon.
Another photograph appeared to show some of the people wearing orange lifejackets as they were taken to shore in a Border Force rigid-inflatable boat.
A boat which appears to have been used by the migrants during their crossing was also being tugged.
A spokesman added: “We are only concerned with preservation of life, rescuing those in trouble and bringing them safely back to shore, where they will be handed over to the relevant partner emergency services or authorities.”
The Home Office said further details would be given later.
