A 43-year-old, arrested on suspicion of arson in connection with the fire at the George Bryan Medical Centre in Tamworth on Monday night, has been released under investigation by Staffordshire Police, pending further enquiries.
Police were called at 9.15pm to the centre on Plantation Lane, Mile Oak, Tamworth.
The facility is run by the Midlands Partnership NHS Foundation Trust and provides mental health services for adults, including acute care under the Mental Health Act.
All occupants and staff were evacuated and there are no reported casualties.
Patients were transferred to other local medical centres.