One migrant has died after a dinghy “deflated” in the Channel, plunging dozens of people into the water.
A Coastguard helicopter has been scrambled, along with lifeboat crews and Border Force personnel.
Kent Police said a woman died in the tragedy.
A source told the Daily Express the dinghy deflated as it reached UK waters.
A Government spokesperson said: “We can confirm that Border Force responded to reports of a migrant boat in distress in the Channel at 1245 this afternoon. One passenger was found unresponsive and was given CPR. Sadly, we can now confirm that this individual has died.
“We are shocked and saddened by this tragic incident. Our immediate thoughts are with all of those who have been affected.
“This latest tragedy underlines the terrible dangers of small boat crossings, and we continue to do everything we can to prevent callous criminals exploiting vulnerable people.”
The RNLI have confirmed their involvement in “incidents in the Channel” on Tuesday afternoon.
An RNLI spokesperson said: “RNLI lifeboats have been tasked by HM Coastguard to incidents in the Channel today.”
Two coastguard vans and ambulances are waiting to receive migrants at the Port of Dover.