The Japanese spa industry is recovering from revelations that the water at many of the country’s most celebrated onsen – or Japanese hot spas – is in fact nothing more than warmed up tap water.

Onsen are a way of life in Japan and spa towns such as Ikaho and Shirahone rely heavily on tourists for their income, lured in by the famous hot spring baths.

However, according to the Asahi Shimbun, one Japan’s leading newspapers, tourists have been mislead over the source of the purported therapeutic bathing water.

The newspaper reported that cases of spas filling their pools with heated tap water have emerged in at least 11 regions, including Gunma and Kanagawa.

In Ikaho, a local tourism company operates 56 spas but only 29 of them use water from a source that is traditionally associated with an onsen.

The news could cost the spas their future: Asahi Shimbun reported that approximately 4,000 tourists had cancelled their reservations to onsen within two weeks of the news getting out.