On Lap 32 of 71 Magnussen was snaking his Haas through the Esses in the second sector when he appeared to suffer a left-rear suspension failure, which sent his car hard into left-hand barriers at Turn 9.
The heavy hit destroyed Magnussen's car, but the Dane was able to climb out of his wrecked Haas unaided.
After a brief safety car period the race was red-flagged with 36 laps remaining, due to the enormous amount of debris.
In a statement before racing resumed, a Haas spokesperson said: "Magnussen is ok.
"He is being kept in the medical centre for a bit longer just as standard observation. When he’s released I’ll advise on pen timings - suspect it might be towards the end of race. The incident looks to be a suspension failure, possibly heat-induced."
Max Verstappen reacted to Magnussen's crash by pitting for new hard tyres but retained his lead ahead of Ferrari's Charles Leclerc and Mercedes driver Lewis Hamilton.
Carlos Sainz was running fourth in the second Ferrari followed by AlphaTauri's Daniel Ricciardo, who comfortably kept up with the frontrunners' pace in the top five.
The race was set to resume at 15:14 local time with a standing start, with all drivers allowed to freely swap their tyres.
That's bad news for McLaren's Lando Norris and Williams man Alex Albon, who pitted after the safety car came out on dropped several positions each.
AlphaTauri's Yuki Tsunoda was the biggest benefactor of the red flag, having moved up from 18th to eighth following an early pitstop.
Earlier on, Sergio Perez shocked the home fans by crashing out in Turn 1 of the first lap after contact with Leclerc.
Leclerc sustained front wing damage in the clash, with the stewards investigating whether or not the Ferrari man was driving around with an unsafe car.
The Monegasque driver's dangling front wing endplate finally broke off in Turn 1 on Lap 4, which caused a virtual safety car.
The collision gave Verstappen free rein to swoop into the lead after starting behind both Leclerc and Sainz, with the Dutchman chasing a 16th victory of a crushingly dominant 2023 season.
Meanwhile, Perez a deflated Perez acknowledged he took a risk from fourth on the grid to try and lead his home race.
"I'm sad, without a doubt because today was my opportunity. I had a very good start and I was only thinking of winning the race. I didn't want to be on the podium," he said.
"I saw the opportunity and I went for it. In hindsight, I took a risk, but if I had pulled it off I would have come out of Turn 1 in the lead."
