F1 teams are forbidden from making changes to their car’s set-up, apart from to the front wing angle, from the start of qualifying, under what are known as parc ferme regulations.
The part in question that could be adjusted was the so-called ‘bib’ or ‘tea-tray’, which is the front of the floor in the middle of the car.
An FIA statement said: “Any adjustment to the front bib clearance during parc ferme conditions is strictly prohibited by the regulations.
“While we have not received any indication of any team employing such a system, the FIA remains vigilant in our ongoing efforts to enhance the policing of the sport.
“As part of this, we have implemented procedural adjustments to ensure that front bib clearance cannot be easily modified.
“In some cases, this may involve the application of a seal to provide further assurance of compliance.”
Red Bull’s drivers’ championship leader Max Verstappen said the changes to their car would have no impact on performance.
Verstappen said: “For us, it was just an easy tool. When the parts were off, it was easy to adjust. But once the whole car is built together, you can’t touch it. So, for us it doesn’t change (anything).
“When I read it, I was thinking about other teams doing it. And then I found out it was related to our team. We never even mentioned it in the briefings, it was just an easier tool to adjust stuff.”
McLaren’s Lando Norris, who is challenging Verstappen for the drivers’ title, said: “It’s one thing having it on your car and another how much you exploit and use it, which we have no idea on.
“If they have been using it in the way people think they have, maybe it will shift things, but they have not got several poles and wins just for such a device. I don’t think it will change anything. But when you see poles decided by thousandths, you might say maybe it will change something.”
Sources close to the situation say the FIA was informed of the device on the Red Bull over the course of the Singapore Grand Prix weekend last month.
Rivals had seen its existence in what are known as open-source component documents that teams have to provide to the FIA about the design of their cars.
The ability to adjust the floor of the car would enable teams to better balance the demands of qualifying and racing.
A team would prefer the car to run lower in qualifying and higher in the race.
The F1 season resumes this weekend after a four-week break with the United States Grand Prix at Austin’s Circuit of the Americas.