Soundings were taken in the Dordogne river around the wreckege of the Robinson R44 on Sunday night but no bodies have been located since that of Lam's son, 12-year-old Shan Yu Kok, was found on Friday night.
A helicopter was due to fly along the river on Monday to see if any bodies have been carried downstream.
The accident happened as Lam was flying over a prestigious Bordeaux winery that he had just bought.
His financial adviser in France, Peng Wang, and James Grégoire, who was selling the château and piloting the helicopter, are also missing.
Gendarmes on Monday planned to place balloons around the wreck and inflate them simultaneously so as to raise it out of the water without destroying any clues to the reason for the crash, which remains a mystery.
The sale of the 65-hectare Château de La Riviere vineyard for an estimated 30 million euros was the biggest Chinese investment in Bordeaux so far.