Hamilton and Leclerc, who finished second and sixth respectively in the race won by Max Verstappen, are being investigated by the stewards following a plank wear inspection in Austin.
The FIA note reveals that the cars of Verstappen and Lando Norris were also inspected, but passed the checks.
The report from FIA technical delegate Joe Bauer states: “A physical floor and a plank wear inspection was carried out on car numbers 16 [Leclerc] and 44 [Hamilton].
“The skids located in this area are found to be not in compliance with Article 3.5.9 e) of the 2023 Formula One Technical Regulations.
“I am referring this matter to the stewards for their consideration.”
Both Mercedes and Ferrari have been summoned to see the stewards.
The section of the rulebook referred to reads: “The thickness of the plank assembly measured normal to the lower surface must be 10mm [plus or minus] 0.2mm and must be uniform when new.
“A minimum thickness of 9mm will be accepted due to wear, and conformity to this provision will be checked at the peripheries of the designated holes.”
Breaches of technical checks of the car often result in disqualification, with a recent example being Hamilton from qualifying in Brazil in 2021.
The seven-time world champion was already in hot water after crossing a live track at the last race in Qatar and was spoken to again in Texas due to his status as a “role model.”
Leclerc started Sunday’s race on pole but, opting for a different strategy, fell behind after Lando Norris stole a march on the Ferrari at the start.
Hamilton, meanwhile, came close to victory after reeling in Verstappen at the end. The 38-year-old has now not won in nearly two years, with his last victory coming in Saudi Arabia in December 2021.
A disqualification would mean Hamilton loses 18 points in the championship standings, while Leclerc would lose eight points.