The Dane was pitched off the road on lap 32 by a suspected left rear track rod failure when the car was under load in the fast right-hander at Turn 8.
Magnussen climbed out of the car unaided, but damage to the barriers led to a red flag. He was taken to the medical centre, but he was passed fit and soon returned to the paddock.
Brake temperatures are always on the limit in Mexico, and in Magnussen's case, they got too high as he was defending hard from Logan Sargeant, and winding the bias to the rear.
The American got past just a few corners before the crash, at which point Magnussen was told by his engineer that he had to get brake temperatures under control.
After the impact, TV pictures showed a brake fire starting around the left rear of the wrecked Haas.
During the red-flag period, the team checked the sister car of Nico Hulkenberg, but no signs of any problem were found, and the German was able to complete the second part of the race.
"It was a heat issue which caused a suspension failure," Steiner told Autosport. "It was heat from the brakes.
"Kevin was defending, and it tipped over. It was just because of the high temperatures here. We just need to manage it better. Nico's car was OK."
Source: Autosport