A chemical analysis of the water of the Banganga Tank in Mumbai`s Walkeshwar area, in which a large number of fish was found dead last month, has found oxygen deficiency as the probable cause, a civic official said on Tuesday.

The tank, which witnesses several religious rituals due to its historical significance, was the site of hundreds of dead fish last month, with the official adding that the fisheries department had also opined that the water-body was overpopulated with fish.