Carlos Sainz edged out Lando Norris in another tight practice session ahead of qualifying for the Spanish Grand Prix.
The top four were split by less than one tenth of a second with Charles Leclerc in third and Max Verstappen in fourth but the session ended with some drama at the end, when Leclerc made contact with Norris.
Leclerc was on a fast lap and appeared to be unhappy about being impeded by Norris, so slowed down and moved left, making small contact with the McLaren driver.
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Just moments later Leclerc, Verstappen and Sainz all nearly tangled, with the first Leclerc-Norris incident under investigation by the stewards.
Mercedes' George Russell and Lewis Hamilton were in fifth and sixth but both drivers are also on the fringe of being in the hunt for pole in qualifying, which is at 3pm on Sky Sports F1 and Sky Sports Main Event.
Ahead of final practice, a fire broke out at McLaren's hospitality and Sky Sports News understands that at least two fire staff personnel were treated for smoke inhalation but their condition is not thought to be serious.
Narrow margins at the front
All weekend, there has been little to separate Ferrari, McLaren, Red Bull and Mercedes, even though the gaps were expected to increase at the front due to the track layout.
Sainz was 0.030s ahead of Norris on the last soft tyre runs in final practice, with Leclerc only 0.037s behind his Ferrari team-mate.
Verstappen, who has a fourth power unit in his car this weekend, so is on the verge of needing a grid penalty for using a fifth engine, was 0.074s behind Sainz but has shown he can produce when it matters most this year.
Russell set the pace in the first half of the session but dropped to fifth at 0.174s behind, with Hamilton in sixth after not putting a clean lap together.
Sergio Perez has a three-grid place penalty for Sunday's race, after driving back to the pits last time out in Canada with a damaged rear wing, and could be starting in the midfield as he's been lacking performance all weekend.
The Mexican was three-quarters of a second slower than Sainz, ahead of Williams' Alex Albon, Aston Martin's Fernando Alonso and McLaren's Oscar Piastri.
Several drivers under investigation
Leclerc is hoping to repeat his Monaco heroics where he converted pole into a win, but could be hit with a grid penalty.
His swerve towards Norris on the run down to Turn Seven was described as a moment of "road rage" by Sky Sports F1's Karun Chandhok.
He is meeting the stewards to explain his actions after being frustrated at alleged blocking from Norris, then came across Verstappen and Sainz also having their own incident, without colliding, on the run down to Turn 10.
Earlier in the session, Lance Stroll had a similar incident where he made contact with Hamilton as he also showed his anger at alleged impeding.
They will also meet the stewards ahead of qualifying.
Sky Sports F1's live Spanish GP schedule
Saturday June 22
1.10pm: F2 Sprint
2.10pm: Spanish GP Qualifying build-up
3pm: Spanish GP Qualifying
5pm: F1 Academy Race 1
Sunday June 23
7.45am: F1 Academy Race 2
9am: F3 Feature Race
10.30am: F2 Feature Race
12:30pm: Grand Prix Sunday: Spanish GP build-up
2pm: The SPANISH GRAND PRIX
4pm: Chequered Flag: Spanish GP reaction
Formula 1 heads back to Europe as the championship moves on to Barcelona for the Spanish Grand Prix and the start of a triple-header. Watch every session at the Circuit de Barcelona-Catalunya this weekend, live on Sky Sports F1. Stream every F1 race and more with a NOW Sports Month Membership - No contract, cancel anytime