Something smells very rotten in the River Tiber's waters

Something is poisoning the fish in the River Tiber, and magistrates haveopened a criminal inquiry, suspecting the dumping of toxic waste, writesRory Carroll

For a city of baked, parched summers, this has been a strange one. Several times a day the sun falters, clouds turn inky and thunderous showers drench all, giving Rome an unseasonal freshness. Stand on a bridge and you can hear the Tiber rushing below, swelled by the rains.

Better not to look down or inhale. The river has turned a dark, bruised brown and that silver glint, so brilliant in the afternoon sun, is a mass of dead fish.

Lining the banks are homeless men, hoping to scoop up a free supper of eel, mullet or carp, and environmental investigators, hoping to find out why the Tiber is sick. Not in a generation has it so worried and mystified the authorities. They have mobilised a helicopter to take aerial photos, dinghies to patrol upstream and teams of scientists to collect and analyse samples. And still they do not know what is wrong.

Something is poisoning the fish, but what? One theory is that the heavy rains have washed toxic earth into subsidiaries feeding the Tiber. The Aniene, a river traversing industrial areas, could be the guilty stream. Another suspect is overflow from the Castel Giubileo dam.

Activists from the Marevivo (Living Sea) organisation suggest a more sinister cause: somebody is taking advantage of the rains to dump toxic substances. Organised crime controls several waste-disposal firms and Italy's industrialists are not known for voting Green.

Whatever the cause, its effect has been so devastating because 30 years of cumulative pollution have left the Tiber's ecosystem fragile and vulnerable.

The scientists say they should soon know the cause but magistrates have already opened a criminal inquiry. Poisoned or not, vagrants and impoverished immigrants on the Tiber's banks are cooking fish over open-air fires while environmental activists with nets transfer living fish into fresh water containers.

This is just the latest of the Tiber's maladies. Once it was the artery to antiquity's capital, a snaking current which ferried barges of corn, wheat, marble and stone from the Mediterranean to the emperors. It passes through one of the world's most beautiful cities, a compact jewel perfect for walking, yet today the river's contribution to leisure and commerce is as dead as its shoals.

A few modern barges posing as restaurants and discos are moored near the Vatican and if you are patient, you might see some people strolling and cycling on the banks. Otherwise it is an ignored, neglected resource, its banks littered with Coke cans, water bottles and cigarette packets.

Where London and Paris have invested thought and money into exploiting their rivers, the Tiber is wasted. Benito Mussolini did build some walkways and steps - which form the shape of an eagle - but his post-war successors seldom matched rhetoric with action. It is the responsibility not of the mayor of Rome, who can be dynamic, but the provincial authorities.

The good news for Romans is that their drinking water remains clean and bountiful, unlike the Milanese, whose drinking water is polluted, and Sicilians, who are lucky to have any. The shock could galvanise a major clean-up of the Tiber, but don't bet on it. Keeping fish alive is not the priority. Despite the rains, the gravest risk to the river is drought. Last year its source in Tuscany was reduced almost to a trickle.

Farmers in Sicily and southern Italy have been in revolt over a dry spell which has withered crops and livestock. Downpours recently have eased the situation, but up till the beginning of August military police were mobilised to stop water theft and the government was considering emergency measures such as rationing, hiking prices and building a pipeline under the Adriatic to pump water from Albania. - (Guardian service)