Were the priests that served in the unsanctioned Temple in the northern kingdom Levites?

Question

I wouldn't think that the Levites would agree to serve in an unsanctioned Temple, often making offerings to Ba'al.

Answer 1

The verse (Kings 1:12:31) is clear that Jeroboam appointed new priests, not from the tribe of Levi:

And he made the house of altars, and he appointed as priests some of the people, who were not of the sons [tribe] of Leivi.