Verbania - A mysterious foam has been floating for several weeks on northern Italy's Lago Maggiore and experts are at a loss to explain what it is and what causes it.

Laboratory tests carried out so far have determined that while the foam is not toxic, it would appear to be related to some form of chemical pollution.

Tests have been carried out on tributaries and drainage into the lake but so far no similar pollution has been found. Experts will continue to carry out tests to determine the composition of the foam in order to decide what measures can be adopted to combat this phenomenon.