Johnny Cecotto Jr looked to have the pace early on, but Leal went quickest with a 1m57.877s - making him the only driver to go into the 1m57s all session.
Stefano Coletti then brought the red flags out having gone wide into the gravel, and spun back onto the road. He did well to avoid contact with the barriers, but was unable to get moving again, and had to end his session early.
After the marshals cleared the stricken Racing Engineering Dallara from the middle of the track, and swept away the gravel strewn across track in the incident, only four minutes remained of the session and no one was able to improve.
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Cecotto finished the session second, 0.1 seconds behind, with Raffaele Marciello 0.3s behind Leal's time in third.
An encouraging start to the weekend for the Lazarus team allowed Nathanael Berthon to end the session fourth, ahead of team-mate Conor Daly in fifth.
Home driver Stoffel Vandoorne and Sergio Canamasas finished sixth and seventh, and Coletti retained eighth position despite his early exit.
Stephane Richelmi and Mitch Evans rounded out the top 10.
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