Authorities said some parts of the airport were reopening on Tuesday, but the departures area of the terminal building remained closed because of the presence of smoke.
Departures from Ciampino, which is used by budget airlines Ryanair and Wizz Air, will continue to be blocked on Wednesday, airport authorities said.
While the fire was reportedly put out in less than a minute, it caused crowds and flight cancellations for most of the day.
Some flights were diverted to Fiumicino airport, on the other side of Rome.
Aeroporti di Roma (ADR) said they believed the fire had been started deliberately, adding they had filed a complaint with local magistrates.
Less than two weeks ago, Ciampino airport was closed and flights diverted after three unexploded World War II bombs were discovered by construction workers.
