Toro Rosso driver Max Verstappen set the quickest time as Formula 1 returned to Mexico City after a 23-year absence.
Verstappen posted a best time of 1:25.990, despite a spin at Turn 1 earlier on, to finish 0.305s faster than Red Bull counterpart Daniil Kvyat.
However, replays showed Verstappen exceeding track limits by cutting one of the Esses on what appeared to be his flying lap.
Ferrari's Kimi Räikkönen was third quickest, having matched Kvyat’s lap time.
Sebastian Vettel was fourth, ahead of Red Bull’s Daniel Ricciardo and Mercedes driver Nico Rosberg.
Rosberg had to abandon his initial run after his rear brakes caught fire but he was able to return to action and go sixth.
Valtteri Bottas was one of several drivers to go wide en-route to seventh as the field struggled with the low-grip conditions, having used Intermediate tyres early on in the session.
Carlos Sainz Jr. was eighth, leaving home favourite Sergio Pérez and Felipe Massa to round out the top 10.
World Champion Lewis Hamilton had a low-key session and placed 11th.
Marcus Ericsson was 12th, ahead of Pastor Maldonado, Felipe Nasr and 2016 Lotus driver Jolyon Palmer.
Nico Hulkenberg was 16th, while McLaren endured a difficult session with Fernando Alonso in 17th and Jenson Button undertaking limited running on his way to 19th.
Manor Marussia's Alexander Rossi was 18th, with Will Stevens suffering a sensor problem in 20th.