Red Bull are investigating a complaint against their Formula One team boss Christian Horner, the Austrian energy drink company said in a statement on Monday without giving any details about the allegations.
The Briton presided over the most dominant season in Formula One history last year, with Max Verstappen taking his third title in a row and the team winning 21 of 22 races.
"After being made aware of certain recent allegations, the company launched an independent investigation," Red Bull said.
"This process, which is already under way, is being carried out by an external specialist barrister. The company takes these matters extremely seriously and the investigation will be completed as soon as practically possible.
"It would not be appropriate to comment further at this time."
The Times newspaper reported Horner, 50, had been accused of inappropriate behaviour by a female colleague, who complained to the team's parent company.
There was no comment from the team but Horner, who is married to former Spice Girls singer Geri Halliwell, told Dutch newspaper De Telegraaf that he completely denied the allegations.
Arsenal's Leandro Trossard capitalised on dreadful defending to secure a 1-0 win against Manchester United that saw the Gunners climb back to the top of the Premier League, ensuring the title race will be decided on the final day.
UAE Team Emirates rider Tadej Pogacar has retained his overall lead after Dutchman Olav Kooij won stage nine of the Giro d'Italia on Sunday, pipping Jonathan Milan by half a wheel right at the finish line in a breathless sprint at the end of a 214-km ride from Avezzano to Naples.
Rory McIIroy claimed his fourth Wells Fargo Championship after a superb back nine saw him finish -17 par having trailed by two shots after seven holes.
Alejandro Tabilo claimed the biggest win of his career beating world number one Novak Djokovic 6-2 6-3 in the third round of the Italian Open, two days after the Serbian was hit on the head by a water bottle.
Norwich City and Leeds United played out a goalless draw in the first leg of their Championship play-offs semi-final tie as both teams seek a return to the Premier League.