Mthembu's contract with Stars is set to expire at the end of June, having initially joined the club from Chiefs in August last year.
The 30-year-old scored five goals and provided three assists in 30 appearances in all competitions for the Nedbank Cup champions.
Ea Lla Koto have been running the rule over fellow hitmen Eleazar Rodgers, Maboke Matlakala and Linda Bhengu, who played for Mthatha Bucks and is the younger brother of ex-SuperSport United forward Phumelele.
"Rodgers and Bhengu started training with the club yesterday," says a source at the Absa Premiership outfit.
"The club is still yet to make decision on Siphelele Mthembu."
Rodgers and Matlakala appear to have convinced management they will add value in Bethlehem.