Van Graan has previously worked alongside ex-Springboks coach Heyneke Meyer, who is one of the favourites to succeed sacked head coach Mike Ford.
Meyer left his South Africa post after the 2015 World Cup, but Van Graan retained a role with the national side.
Following Ford's departure on Monday, Bath said a "further announcement" was expected in due course.
However, they have yet to comment further.
Premiership club Bath are set to appoint South Africa assistant coach Johann van Graan in a coaching role.