The fire services responded to a call from the Ministry of Social Development and Family Services on Tuesday morning.
In a statement the ministry said around 9.30 am a member of staff alerted the building security staff to the smell of smoke.
Fire services were called and the building evacuated.
Officers from the Wrightson Road fire station did an assessment before giving clearance for staff to re-enter the building. The incident resulted in a traffic pile-up, as the lower part of St Vincent Street was cordoned off while fire officials searched for the source of the smell.