The building of the National Health Insurance Fund (NHIF) in Sofia was evacuated after a report of an explosive device, Sofia police told the BTA news agency. Police are following standard procedure.
A BTA reporter saw visitors and staff leaving the building.
The Interior Ministry says there are also reports of explosive devices at other places in Sofia, but it has not said where.
Similar reports about kindergartens and schools in the capital came in at the start of this month. Alerts were also raised then in Burgas, Shumen, Lovech and Razgrad.