Palma's municipal services company Emaya insisted on Wednesday that the Parc de la Mar lake in front of the Cathedral is cleaned on a daily basis and that its water quality department had not reported any "alteration" to the water.
Emaya was responding to the fact that part of the lake had taken on a grey hue and that there was sludge floating on the surface.
There had apparently been "no anomaly" to explain what looked as if it could have been algae.
Both the town hall and Emaya said that there had been no incident with pipes.