However, Bastia went into the interval with a 2-1 lead as Francois Modesto headed in the second minute of first-half injury time.
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Toulouse tried to press for an equaliser as the second half progressed and went close through Martin Braithwaite and Ben Basat, but were reduced to 10 men with 15 minutes of normal time remaining following the dismissal of Clement Chantome.
Abel Aguilar had a late chance for the home side, but it was Bastia who scored the game's fourth goal in injury time.
Ben Basat brought down Wahbi Khazri inside the box, and Gianni Bruno successfully converted the resulting spot kick.
The result means that Bastia move up to 10th in the league table, while Alain Casanova's Toulouse are 12th.