FIA Technical Director Tim Goss has revealed F1's governing body had originally only planned to inspect Lewis Hamilton and Charles Leclerc's cars at the United States Grand Prix.
The Mercedes and Ferrari drivers' were disqualified after the event with the FIA Technical Delegate having found the skid blocks to be non-compliant on each of their cars.
Max Verstappen's Red Bull and Lando Norris' McLaren were also checked and subsequently passed, ensuring their podium finishes remained valid.
Hamilton has questioned the validity of the checks, however, with the seven-time F1 champion indicating his sources suggested over half the field was non-compliant.
Explaining the inspection process to Sky Sports F1, Goss said: "We selected two cars for our post-race check and inspected those.
"The check takes a while. We found they were the wrong side of the regulations and that caused us some concern.
"What we wanted to do was try to understand whether the problem was systematic and something to do with the conditions of that race, so we decided to then select another two teams, another two cars, which happened to be Verstappen and Norris, and check those.
"After we checked those two cars and found that those two were the right side of the limit and all fine."
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Beyond sticking a ruler or depth gauge into a hole
With a 50 per cent pass rate from the four inspections, questions had been raised as to whether all cars should have been checked for compliance.
"It is beyond just sticking a ruler or depth gauge into a hole and measuring a skid thickness," explained Goss.
"We actually have to disassemble part of the car and the check takes about half an hour to do. If we had two crews doing that, then what we are looking at is about five hours of work to check all the cars, after which you are reporting cars to the stewards.
"So then maybe the race result comes out six, seven or eight hours after the race has finished and I don't think that is acceptable for the sport."