Ferrari driver Sebastian Vettel topped the first Formula 1 free practice session for the 2017 Bahrain Grand Prix.
While Ferrari team-mate Kimi Raikkonen was slowest after stopping on his seventh lap with smoke coming out of the rear of the car thanks to a problem the team suspected was related to high engine temperature, Vettel had no such trouble.
Vettel's best time of 1m32.697s, set with 31 minutes of the session remaining, was enough to guarantee top spot by four-tenths of a second ahead of Red Bull driver Daniel Ricciardo.
During the early running with each driver using their first set of tyres, which can only be used during the first 40 minutes, Valtteri Bottas was fastest for Mercedes after setting a time of 1m35.002s.
That put him 1.077s faster than Toro Rosso's Carlos Sainz Jr, as the pair were the only drivers to opt for the soft Pirellis for their first sets.
Hamilton was the quickest of those who used mediums for their early running, 1.7s slower than Bottas, but he was the first of them to switch to softs.
This allowed him to hit top spot 37 minutes into the session with a lap of 1m34.636s, as none of his leading rivals took a second set of tyres so early.
As the rest of the field switched to softs, Williams driver Lance Stroll, with a 1m34.895s, and then Force India's Sergio Perez, with a 1m34.322s, both had stints at the top of the timesheets.
Vettel, who was fourth fastest during the first 40 minutes, then banged in his quickest lap of the session to take a top spot he would never lose.
Ricciardo and team-mate Max Verstappen slotted into second and third respectively shortly after Vettel set his time, with almost half-a-second separating the Red Bull pair.
Perez's time was good enough to end the session fourth ahead of Williams driver Felipe Massa, who had jumped ahead of team-mate Stroll moments after the Canadian had been knocked off top spot.
Massa had a dramatic spin at Turn 13 late in the session as a result of a major lock-up thanks to a problem with the brakes, but was able to recover to the pits.
Esteban Ocon was seventh fastest for Force India ahead of Fernando Alonso and Romain Grosjean, with Hamilton ending up the best-placed of the Mercedes drivers down in 10th place.
Daniil Kvyat was 11th fastest despite complaining about understeer, and was just under a tenth faster than Renault's Nico Hulkenberg, who ran wide and off the track at the final corner on his quickest lap of the session.
McLaren driver Stoffel Vandoorne was 13th, but his session came to a premature end with 21 minutes to go after, according to the Belgian, "the engine stopped".
Bottas, who concentrated on long runs for much of the session, was down in 15th and 2.305s off the pace.
Haas driver Kevin Magnussen and Sauber's Marcus Ericsson were 16th and 17th ahead of Pascal Wehrlein.
The Sauber driver, in an F1 car for the first time since Friday practice at last month's Australian Grand Prix, completed 23 laps during the session and was only 0.7s off his team-mate.
By the end of the session, Sainz had been shuffled down to 19th after not improving on his early soft-rubber pace, ahead only of Raikkonen.
BAHRAIN FP1 TIMES