A bus bringing retired police officers to a national convention veered off a highway in northern Italy on Saturday and plunged into a canal, killing at least five people, officials said.

More than a dozen others were injured, some of them seriously, when the bus broke through the barricades of the A13 highway near Padua and ended up partially submerged in water, firefighters and news reports said.

Rescue crews recovered five bodies and extracted several other injured passengers from the bus, Padua firefighter Mauro Bacelle told Sky TG24 television.

Police divers were brought in to ensure no victims were thrown into the canal, the LaPresse news agency said.

Bacelle said the stretch of the highway where the crash occurred isn't particularly risky and that the crash occurred well after daybreak, at around 8 a.m.

The bus was bringing retired carabinieri paramilitary police officers from Aprilia, south of Rome, to a national carabinieri convention in Jesolo, near Venice, reports said.