The McLaren team on Monday hinted that rivals Red Bull had used coded messages to assist Australian Daniel Ricciardo's drive to a podium finish in Sunday's Singapore Grand Prix.
McLaren's racing director Eric Boullier said he and his McLaren colleagues had listened keenly to other teams' messages during the race. (Also read: How Hamilton won Singapore Grand Prix)
Asked how different it was to work on the pit wall following the clampdown on radio communications, he said: "Nothing, but it makes us more busy listening to the others to see they are not doing anything like Red Bull did twice on Ricciardo.
"I think it was coded, yes. It is up to the FIA to investigate, so it is not for me to say anything.
"But it was a strange message. Once would have been OK, but twice or three times is a bit strange."
Red Bull team chief Christian Horner said his team had clarified with F1 race director Charlie Whiting what messages it could use with Ricciardo.
"Obviously we spoke to Charlie and told him Daniel had some reliability issues," he said.
"That was why he was told to stay off the kerbs because that was causing damage to the battery. I think that was sensible and it's about trying to find a balance with this radio ban."