Prosecutors in Sardinia have opened five investigations into the deaths of 16 people killed during flash floods which swept away bridges and flooded homes, Italian media reported Sunday.

One person was still officially registered as missing after the Mediterranean cyclone which swept through on Monday, leaving the port city of Olbia, a popular holiday destination in the summer months, under water and thousands of people homeless.

The deaths sparked angry accusations that the island had not been sufficiently forewarned or prepared for the sudden deluge of 440mm (17.3 inches) of rain -- almost half the amount that usually falls on average in Italy over an entire year.

Sardinia's fire brigade said trucks had been stuck in flooded areas, forcing them to wait for more equipment to arrive from the mainland.

Case files have been opened into those who died in Olbia, including two children, as well as victims who drowned when a bridge gave way in nearby Monte Pinu and a policeman who died in his car after a section of the road he was driving on collapsed.

The officer had been escorting an ambulance which was rushing a pregnant woman to hospital.

Italy's Environment Minister Andrea Orlando on Sunday announced an extra five million euros ($6.7 million) in funds for the stricken island, on top of 20 million euros already released by the government.

Infrastructure Minister Maurizio Lupi said the government would be looking into "whether intervention protocols should be improved" after the flood.

"Families in Sardinia have told me they had never seen such rain. In one hour, hell broke lose. This cannot become an excuse for not doing anything," he said.