Investigators have opened a criminal investigation into work conditions at the Technocentre in Guyancourt, outside Paris where the three employees worked.
The prosecutor's office in Versailles said they intended to look into offences such as harassment, which may be linked to the death.
Three weeks earlier, plant employees held a silent march in memory of two colleagues who had committed suicide in October and January in Guyancourt.
"Each one of us must reflect on our share of responsibility"
Renault management statement
One of the employees threw himself from the fifth floor of a building at the plant.
Jean Hotebourg, a union official, said that another employee drowned in a nearby pond after leaving his computer screen displaying an account of a bitter exchange with management representatives.
Hotebourg accused management officials of "harassing" employees, saying they had been humiliated when their boss criticised them in front of colleagues.
Renault said in a statement that "there was no correlation, for the time being, between work conditions" and the three suicides.
"We have impassioned engineers who conceive vehicles and it is very difficult to draw a link between the workload and the Renault contracts for 2009," said a management statement.
Renault has announced plans to roll out 26 models including 12 new ones by 2009.