Thane, May 11 -- The cleaning of sewage tank in Thane's residential society, which led to three deaths on Friday, was not carried out according to the standard protocol of the sewage treatment department, said Thane Municipal Corporation (TMC) officials.

According to civic officials, a sewage tank should not be cleaned manually. In case of manual cleaning, the workers should be provided with proper safety gear before entering the tank. Moreover, every septic tank should have outlets to release harmful gases to prevent suffocation.

"We clean the sewage tank using suction and centrifugal pumps. The tank should first be de-watered, after which the residual slurry needs to be dried out. This ensures there are no harmful gases in the tank. We ...