Sauber and team principal Monisha Kaltenborn have parted ways, according to Sky sources.
Kaltenborn has been the Swiss outfit's CEO since 2010 when Peter Sauber rebuilt the stable he had sold to BMW five years earlier, and she was even a part owner of the team after buying shares in 2011.
In 2012, Kaltenborn became Formula 1's first female team principal but she has now left her Sauber post with immediate effect, meaning the team currently ninth in the constructors' standings have no boss heading into the Azerbaijan GP, live on
Sky Sports.
Peter Sauber sold his controlling stake of the team to Longbow Finance last year and
Sky Sports News HQ's Craig Slater reported that the Swiss based investment firm wanted to bring in their own individual to run the team on a day to day basis.
"There is significant speculation that what caused her to leave the team is that she wanted equal treatment between the two drivers Pascal Wehrlein and Marcus Ericsson," Slater reported from Baku.
"Whereby the team's owners wanted to give preferential treatment to Ericsson, the Swede, who is closely linked to the group that bought the team."
During her time in charge, and since becoming an independent team again seven years ago, Sauber have struggled to deliver consistently as a midfield outfit, with their only two podiums coming in 2012.
Kaltenborn oversaw one of F1's strangest scandals in 2015 when Sauber technically went into the season-opening Australian GP with three main drivers as Giedo van der Garde claimed he was signed up for the upcoming campaign.
Sauber stuck to their new partnership of Marcus Ericsson and Felipe Nasr in Melbourne and for the rest of the year, and had to pay Van der Garde a significant compensation fee for him to relinquish his contract.
Eighth and tenth-placed finishes in the Constructors' Championship have followed that dispute, with Sauber's only victory coming in 2008 thanks to Robert Kubica's Canadian GP triumph.
Sauber have endured years of financial troubles and, amid speculation that they could fold, Kaltenborn oversaw the sale of the team to Longbow Finance last year. Though she kept her post as CEO and team principal at the time, owner Peter Sauber stepped down.
After the Manor F1 team left the sport at the end of 2016, Sauber were expected to be the backrunners this season - though Pascal Wehrlein's crucial four points in Spain means McLaren are currently at the bottom of the standings.