A Cadillac-triggered red flag punctuated the opening hour of running on day two of Formula 1's first of two pre-season tests in Bahrain.

Sergio Perez was understood to have parked his Cadillac on the back straight out of Turn 10 on the outlap.

His stoppage triggered a three-minute red flag, though it took longer than that for the stricken car to be brought back to the pits, presumably via service roads.

Cadillac had logged over 100 laps on the opening day - and Perez was back out on track after the Thursday morning stoppage before the first our was out.

It was otherwise a largely inconspicuous first hour, with teams by and large limiting themselves to out-and-inlaps and other very short runs.

A couple of push lap runs on hard tyres lifted first-day pacesetters McLaren and Lando Norris well clear again, nearly two seconds ahead on a 1m35.795s as the first hour concluded.

Just after the hour mark, Charles Leclerc produced the quickest time of the test so far to eclipse Norris, with a 1m34.442s.

Pierre Gasly in the Alpine was the most prolific in terms of mileage in the first hour, logging 20 laps at the time of publishing.

None of the cars that had major issues in the afternoon of day one, Mercedes - which did get back on track late-on yesterday - Racing Bulls and Aston, ran extensively in the first hour, but all three did run at least briefly.