They were both transported to Montreal's Sacre Coeur hospital for checks and later released with no injuries.
Both Williams and Force India pointed the finger of blame. Williams' post-race press statement said Perez "crashed into" Massa, but Force India claimed Perez was "the innocent victim".
Ultimately, the stewards sided with Massa, penalising Perez five places on the forthcoming Austrian grand prix grid.
According to Germany's Auto Motor und Sport, however, Force India suspects a conspiracy.
That's because, in addition to the four stewards in Montreal including former driver Derek Daly, also in the stewards room on Sunday was Adrian Fernandez.
Former Indycar driver and Mexican Fernandez was Perez's manager until two years ago, when they acrimoniously split.
"The driver steward was Derek Daly," said Force India team manager Andy Stevenson. "I don't know why Fernandez was asked for his opinion."
FIA race director Charlie Whiting insisted: "From time to time, there are observers to the stewards.
"Fernandez will be the driver representative in Russia, so we invited him here to have a look."
Whiting said any talk of an anti-Perez conspiracy is "nonsense".