Swiss police are investigating an alleged robbery amid reports that the four-times Formula 1 world champion Alain Prost was injured during a home invasion.

The Swiss tabloid Blick reported late on Friday that the 71-year-old Frenchman sustained a head injury from intruders who forced his son to open a safe during the incident on Tuesday morning.

“The perpetrators entered the residence while the occupants were present, threatened them, and forced one family member to open a safe before fleeing with the stolen goods,” the public prosecutor’s office said in a statement. “Despite the extensive search operation launched, the perpetrators have not yet been apprehended at this stage.”

The police, who did not name the victim, said “several” balaclava-wearing intruders “broke into the house. Once inside, they threatened the occupants and inflicted minor head injuries upon one family member, under circumstances that remain to be established.

The perpetrators then forced another family member to open a safe before making their escape with stolen items, a precise inventory of which is currently being compiled.”

Blick reported that Prost, who won four world championships between 1985-1993, was “visibly shaken by this brutal intrusion” and that he has left the home in Nyon beside Lake Geneva in the Swiss canton of Vaud.