The European Centre for Disease Prevention and Control announced on Tuesday the detection of unknown-source hepatitis infections in children in four new European countries, two weeks after the UK revealed similar cases on its territory.

The European agency indicated in a statement that "following the acute unknown-source hepatitis cases reported by the UK Health Security Agency in early April, additional cases have been reported in children in Denmark, Ireland, the Netherlands, and Spain."

Nine suspected cases were also identified in children aged between one and six years in the US state of Alabama, according to the European Centre for Disease Prevention and Control.

The centre explained that "investigations are ongoing in all countries where cases have been reported. Currently, the exact cause of hepatitis infections remains unknown," but British investigators "consider that a type of infection most likely caused the clinical and epidemiological characteristics of the cases."

The World Health Organization said on Friday that it expects new reports in the coming days, after reporting "fewer than five" cases in Ireland and three others in Spain.

In response to a query from Agence France-Presse, the European Centre for Disease Prevention and Control did not provide detailed numbers of cases by country.

No deaths have been recorded among the infected, but some British cases required liver transplants.

The European centre clarified that "laboratory tests for the cases excluded infections linked to viral hepatitis types A, B, C, D, and E in all cases."

The United Kingdom reported to the World Health Organization on the fifth of April this year ten cases of acute hepatitis in Scotland, before reporting 74 cases three days later, according to the UN agency.

Among the infections in the United Kingdom, "several cases showed signs of jaundice."