The blast occurred early on Wednesday morning and caused a fire in the building.
At least three people have been injured after a powerful explosion rocked an office building in central Athens.
The blast early on Wednesday morning also severely damaged shop windows on several nearby buildings and sparked a fire.
Fire department officials said a 77-year-old man was hospitalised with burns, while two others had medical treatment for smoke inhalation.
Firefighters were using aerial ladders to search for anyone possibly trapped inside the damaged buildings.
The cause of the blast wasn’t immediately clear, officials said. A crime investigation unit had also arrived at the scene.
The pre-dawn blast occurred 200 metres from the ancient Temple of Olympian Zeus on the busy Syngrou Avenue.