The building was evacuated and though there was some damage no one was hurt in the blaze which sent plumes of smoke billowing out of the building.
"Firefighters have now finished their work, and commission services are looking to re-establish essential services as soon as possible," the commission said in a statement.
"No one can work in the Berlaymont at the moment," said Amadeu Altafaj, spokesman for the European Commission, the EU’s executive arm.
"The technicians must first clean everything and carry out the work" to get everything back in working order, he added.
He said that commission employees were waiting to learn when they could return to their desks, a key question for many who left important papers and personal effects when they evacuated the building on Monday.
Some of the 2,700 people who normally work in the building were working from home on laptop computers, said Altafaj.
The 27 EU commissioners themselves found space in other commission buildings in the area.
The commission’s daily press briefing was also switched to another building.
AFP/Expatica