Sauber: Technical director Jorg Zander leaves team with immediate effect
Sauber have parted company with technical director Jorg Zander.
The Swiss team gave no reason for the German's departure, but said it was with "immediate effect".
Sauber said "until a new organisation" was finalised, the current heads of department would report to team boss Frederic Vasseur.
Zander joined Sauber in November 2016 from a position as technical boss of Audi's now defunct World Endurance Championship programme.
A replacement has not been named.
The 54-year-old previously worked for Sauber in 2006-7 and has held senior positions in a number of other F1 teams.
He was deputy technical director of Brawn when they won the world title in their only season in 2009, before joining Mercedes. He had previously worked for Honda, Williams and BAR.
Sauber, whose rookie driver Charles Leclerc finished sixth in Sunday's Azerbaijan Grand Prix, are ninth of 10 teams in the constructors' championship after four races this season.
They have made significant progress since last season, when they finished last, following the creation of closer links with Ferrari.
They now use current-spec Ferrari engines, rather than the 2016 power units used last season, and carry branding and financial support from the Italian team's sister brand Alfa Romeo.