PSG confirmed in a brief medical statement that Neymar has been diagnosed with "a right adductor strain", while Mbappe has "a bruised right shoulder".
"A 48-hour period of treatment will be undertaken to assess their clinical evolution", PSG said.
Asked if the Brazil worldwide would be available for PSG's next games, Saturday's league encounter against Toulouse and the upcoming Champions League game against Liverpool, Lasmar said: "It's important to wait approximately 24 hours more".
A source told ESPN FC that Mbappe will have X-rays on his shoulder on Wednesday, but that the first diagnosis is reassuring: He did not dislocate his shoulder nor suffer any ligament damage.
Neymar believes the injury he sustained is "nothing serious", while - after the game - Brazil boss Tite would not discuss the injury.
While signs are positive for his availiablity for a crucial Champions League match against Liverpool next week, the source said that he is likely to miss PSG's match against Toulouse in Ligue 1 on Saturday.
But the victory was overshadowed when Mbappe was hurt after falling awkwardly as he challenged the diving Uruguay goalkeeper Martin Campana for the ball.
"He felt discomfort. He will need a bit more time to evaluate it and take a scan, but in principle it is not a serious injury".
Just one point separates the two teams in Group C with only two matches remaining.