French police are questioning a man on suspicion of murder after four bodies were found in the Seine near Paris.
The first victim was spotted by a passer-by near a bridge in Choisy-le-Roi, a south-eastern suburb of the capital, on 13 August. Later that day police searching the area discovered three more bodies immersed nearby.
Prosecutors say that one of the victims was strangled and another showed violent injuries.
The suspect is being held in Paris. Police have given no details about him or how many murders he is being questioned over.
The first body had only been in the water for a short time and was identified as a local 40-year-old man, prosecutors said.
The three others were found in "a very advanced state of decomposition", they added.
The prosecutors stressed there was so far no evidence of a link between the victims. They could have been submerged in separate places upstream and taken by the current to the foot of the Choisy bridge.