In Le Trou (1960), who is responsible for the denouement and why?

In Jaques Becker's Le Trou (The Hole, 1960)

the gang's escape is foiled and it is implied that they blame Gaspard.

However, it does not seem explicit that he is guilty of this. Is the ending intentionally ambiguous or is it clear how and why the guards became aware of the escape plan?

I see various possibilities:

• Gaspard did betray the gang, because:
  • The withdrawl of the accusation was a veiled bribe by the governor for any inside information, and he decided to give the others up to accept and ensure his release.
  • The withdrawl of the accusation was genuine, and he tipped off the governor because he was jealous that they would partake in the daring escape without him while he received an unremarkable release.
• The prison wardens became aware of the escape plans by means unrelated to Gaspard's interview with the governor; Gaspard was loyal to his closest friends but is unable convince them so.