It's reported in the Italian media
here
It basically says that the radar system controlling the North-West of the Italy broke down for the third time in 24 hrs. ENAV announced that it is back on line since 11:14 today and flights are once more operational from all northern airports.
Inevitable delay are occuring, compouded by heavy fog at Rome-Fiumicino.
And a comment that safety was not compromised.