Mkhabela was released by Highlands Park last week together with former Orlando Pirates striker Tendai Ndoro.
The Mpumalanga-born midfielder also played for Platinum Stars and SuperSport United before joining the Lions of the North.
According to a source close to Siwelele, the club has already started planning for next season despite the uncertainty surrounding its future.
"There are players whose contracts are ending this season and some could be sold to other teams, but the club has already identified a few replacements," the source tells KickOff.com.
"Mkhabela is also a target. He is versatile. He can play both in defence and midfield and that's another reason he has attracted Celtic."
Celtic CEO Khumbulani Konco says it is still too early for his club to comment on potential new signings for next season.
"The season has not even completed," says Konco. "How can we talk about new signings?"