It seems to be the same: A luat foc casa or maybe more often Casa a luat foc.
Some random news headlines:
EDIT: on a second thought, all those instances could be (perhaps even better) translated as "a house caught fire", too. That leaves the question, if there is a clear distinction in Romanian between "being on fire" and "catching/having caught fire". (Though I guess one could argue that those two expressions basically mean the same.)
The house was on fire = Casa era în flăcări. If you want to keep the meaning "caught fire" = Casa luase foc.