Radio masts operated by the Vatican's radio station are causing cancer in children, a medical expert has told a Rome court – resulting in six officials of the station being investigated for manslaughter.

The claims of Professor Andrea Micheli, from Milan's National Tumor Institute, focus on 19 child deaths from leukaemia or lymphoma between 1980 and 2003 in the Cesano area, north of Rome; Vatican Radio operates masts nearby in Santa Maria di Galeria.

Micheli, a professor of cancer epidemiology, says in his 300-page report: "The study suggests there was an important, coherent and significant link between residential exposure to the Vatican Radio structures and an excess risk of death from leukaemia and lymphoma in the children."

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He said the raised cancer risk occurred in children under 14 who lived less than 7.5 miles from the masts. He also found evidence of a link between the radiation and adult cancers – but only among those who lived much closer to the antennae.

His investigation was ordered by the court five years ago after concerns were raised about an increased incidence of cancer in the area. As a result of Prof Micheli's evidence, six officials of Vatican Radio have been placed under investigation for manslaughter, by investigating magistrate Stefano Pesci.

The Vatican was quick to point out yesterday that the Italian Navy also operated radio masts in the area.

La Repubblica reported, however, that the leaked court report singled out the Vatican Radio masts as the likely cause, quoting it as saying: "It is due to exposure to the antennae of Vatican Radio and not that of the navy."

Father Federico Lombardi, the director general of Vatican Radio, said it had followed all regulations in setting up the masts.

He also expressed concern that the report was leaked ahead of its official publication,

Vatican Radio, which was set up in 1931, broadcasts to 61 countries in 47 languages.