Another marine mammal has been sighted in the Seine.
According to French media, the beluga whale swam in the Seine, about 70 kilometers from Paris.
The animal is said to be emaciated and to have skin changes, according to the news channel BFMTV.
The state of health was "worrying", said the prefecture of Eure.
The authorities are said to be busy feeding the animal and continuing to persuade him to swim towards the mouth.
Since he shows little on the surface, it is not easy for the rescuers.
"The environment is not very welcoming for the beluga, the Seine is very polluted and the whales are extremely sensitive to noise," said Sea Shepherd's Lamya Essemali.
The Seine is an important shipping route within France.
The beluga is a protected whale species that prefers colder waters.
The Seine is likely to be warmer than usual due to the prolonged heat in France alone.
In France, there have recently been repeated reports of lost whales in the Seine.
Ammunition was found in an orca whale that was discovered dead in the Seine in late May.
The marine protection organization Sea Shepherd has offered a reward of 10,000 euros for any information leading to the perpetrator.
A fin whale also got lost in the Seine.