TRG Imaging on Tutanekai St remains closed following a fire on Sunday that also caused Lakes Primecare and Lakescare Pharmacy to close for the day.
Fire safety investigator John Rewi said the cause of the fire could be electrical but a final conclusion would be released tomorrow.
TRG Imaging has another site on Haupapa St which has been taking on extra patients to help ease the backlog.
The Rotorua Fire Brigade was alerted to the fire about 2.20pm on Sunday. Smoke spread to neighbouring premises and staff and members of the public at the medical centre and the pharmacy evacuated.
No one was inside the TRG Imaging building at the time.
Tutanekai St between Haupapa and Arawa Sts was closed to the public while firefighters got the fire under control.
It is not known when TRG Imaging's Tutanekai St premises will reopen.