Rome police have announced that they may have discovered the cause of a mysterious bitter smelling cloud that has been appearing erratically across the city and upsetting Rome residents over the last week. The authorities were first alerted to a powerful acrid smell on 9 February by residents in the south of the city concerned about whether they could be breathing toxic fumes. The area affected stretched from Centocelle in the north of the zone to Castel Gandolfo in the south. Then on 12 February police received over 50 telephone calls after the smell was noticed again, this time hanging over the west of the city in the Cassia, Grottarossa and Monte Mario areas, but with some people catching whiffs in the centre of Rome around Flaminio, Prati, Esquilino and Piazza Venezia. The fire brigade, the operational ecology unit (NOE) of the police and the regional environmental protection agency (ARPA) began investigating the cause of the odour and initially pointed the finger at gas escaping from the ground after some small seismic movements south of Rome. The second hypothesis was that the foul-smelling cloud was being blown on the wind from the vast Malagrotta rubbish dump to the west of Rome. However, investigating authorities said they now believe the odour to have a less sinister origin: olives. They claim the smell is that of a by-product of olive oil made from pulp and stone fragments blowing over on the wind from an industrial plant 50km outside Rome. Residents have nothing to fear from the foul smelling cloud, however, which was described as