A government spokesperson said: “Border Security Command officers alongside Kent Police have been responding to an incident in Dover.
“Twenty-one individuals have already been detained under a swift enforcement response.
“There is a thorough investigation ongoing and it would be inappropriate to comment further.”
Officials said those who had been detained had been taken to Western Jet Foil for processing.
Migrants crossing the Channel are usually brought to shore by Border Security Command or RNLI boats.
On Tuesday, 154 migrants arrived in three boats, of which one was an uncontrolled landing.
It takes the total of migrants to have arrived in the UK this year to 17,784.
The total so far this year is down 44.7% compared with figures for 22 September 2025, at which point 32,188 migrants had arrived that year.
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