FIA race director Michael Masi believes the drain collapse issue at Portimão that prematurely halted FP3 on Saturday may have been caused by the downforce of F1's cars.
Yesterday's final practice session was red flagged in its final minutes when Sebastian Vettel at Turn 14 and flipped a drain cover out of its mounting.
Subsequent repairs and a thorough check of all the circuit's drain covers led to qualifying being delayed by 30 minutes.
Masi said the drain's dislodging was unusual in that it was the element's concrete casing that had collapsed, an issue never seen before at a track.
"It wasn't actually the drain cover per se, it was actually the concrete case underneath that collapsed," said Masi. "And then what we saw sticking up was the drain cover itself.
"As soon as it was noticed, FP3 was obviously suspended, it couldn't continue, and a repair was undertaken to that area. Further checks were undertaken for a number of other drains at exactly the same point in time.
"It's something we haven't really seen before, a collapse of that nature. So we checked all the other drains with all of the officials around the circuit, that was the most efficient way to get that done.
"There were a couple of other cracks that were identified and repaired immediately.
"And, obviously, where the drain itself was at the Turn 14 on the left-hand side repair was undertaken with putting plastic pipe in and filling it with concrete, and then a quickset concrete on top of that, and trying to get that dry as quick as possible.
"So that meant a slight delay to qualifying. But in the circumstances, better to have that done and everything else checked.
"As soon as the last activity was completed today, further checks were undertaken around the entire circuit for all drains, just as a further precaution."
Masi suggested that the downforce level of F1's current-spec cars, which are visiting Portimão for the very first time this weekend, may have caused the concrete collapse and rupture.
"We probably don't appreciate the forces that an F1 car generates," he said.
"And it was certainly unforeseen, is probably the best way to put it, considering the circuit has had a significant number of upgrades done to it for this event, including the entire resurfacing of the circuit, as well as a number of safety barrier upgrades.
"And all of the drains were also checked at the same point in time."
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