Magnussen was forced to take to the grass to avoid Ricciardo in the dying stages of the final practice hour for this weekend’s Emilia Romagna Grand Prix in Imola.
It was one of a number of near misses in the final minutes following a late resumption after Sergio Perez crashed to trigger a red flag.
With two minutes remaining, drivers headed out with mixed objectives, a point officials noted in their findings.
Magnussen encountered Ricciardo on the run between Acque Minerali and Variante Alta, diving to the grass to avoid contact with the RB, which was passing Yuki Tsunoda.
It resulted in RB being handed a reduced €5000 fine, while Ricciardo was unpenalised.
“The Stewards usually do not investigate “impeding” during free practice sessions unless they are considered dangerous or potentially dangerous,” the stewards noted.
“The incident between Magnussen and Ricciardo was considered by the Stewards as being potentially dangerous, in particular as Magnussen ended up driving into the grass at 225km/h.
“This case is unusual in that it occurred after the checkered flag on the session.
“This means it is not classically “impeding” as it did not prevent Magnussen from setting a fast time.
“It is also therefore understandable that Ricciardo was driving slowly, preparing for his practice start.
“It is also fully within the regulations for Magnussen to be driving at speed, even after the checkered flag.
“The Stewards considered the location of the incident, which was after the crest of the hill leading up to Turn 14.
“There was no chance that Ricciardo was likely to see Magnussen in time, and vice versa. Ricciardo was avoiding his teammate, Tsunoda, who was also manoeuvring to prepare for his practice start.
“This meant that Ricciardo was near the racing line at the time.
“It was also understood by the Stewards that the situation was even more unusual due to the previous red flag, and the resumption of the session giving some of the teams the ability to complete the lap, and others not, but choosing to get the most information possible.
“The Stewards have issued penalties for incidents during Free Practice sessions previously, although those incidents were all prior to the checkered flag.
“Given the circumstances, it was important for the team to give sufficient warning of a fast car approaching, which they failed to do until Magnussen was at the scene.
“This failure caused a potentially dangerous situation.
“The Stewards consider that there are a number of mitigating circumstances, and that this situation is highly unusual, but that nevertheless, the teams have a duty of care, even after the checkered flag.
“Therefore, the Stewards issue a fine to the team, but in view of the mitigating circumstances, a significantly reduced one from previous cases and no penalty to the driver.”
Ricciardo ended final practice 11th, with team-mate Tsunoda 13th.