Red Bull's Daniel Ricciardo suspects a "fundamental" problem with Renault's engine caused all three Renault-powered teams to suffer failures during Formula 1's Mexican Grand Prix.
Ricciardo and Renault's Nico Hulkenberg both retired early from the Mexico City F1 race, before Brendon Hartley's Toro Rosso caused a virtual safety car when it pulled off the track just before half distance, after reporting he was "losing a lot of power".
Hulkenberg had to pull off the track when Renault told him his car was "unsafe", while Ricciardo reported an issue with the turbo as he toured into the pits. The second works Renault of Carlos Sainz was also forced out.
When asked if he thought the issues were related to the altitude or temperatures in Mexico, Ricciardo replied: "Certainly something fundamental [is] going on.
"We've been coming to Mexico the past few years so there shouldn't be any surprises - I know the altitude and temperatures have been hard to stay on top of this weekend.
"I don't know if it's this year's spec of engine, which is struggling up here - obviously it is, but why we're not sure.
"It's been a pretty grim weekend for a few of us, it's a shame to be out early again.
"I guess it's a bit of what Max [Verstappen] experienced early in the year - it's not so fun."
While Verstappen controlled the race from the front to win for the second time this season, Ricciardo charged into the top 10 from 16th position on the grid before his retirement, having taken an engine change and 20-place grid penalty after qualifying.
"Obviously the weekend's turned to crap," Ricciardo added. "I did what I could at the start - it was pretty close, there was a bit going on - but I made quick progress.
"I told Helmut [Marko] this morning that I'd get up to seventh by the end of the first lap. I was a couple of laps off I think, but we got close.
"We put the new unit in, but something went wrong. Not really sure what it was or where that puts us for Brazil."