As per the preliminary reports, an apartment association had hired a private contractor to clean the manhole after a blockage was reported.
The contractor had sent a team of worker's to clean the manhole and during the cleaning process, one worker entered the 10ft deep manhole and slipped.
To rescue him, two more workers entered the manhole, but all three collapsed inside the manhole due to suffocation.
Police and fire service officials reached immediately at the spot and took the persons out of the manhole but all the three were declared dead.
Bruhat Bengaluru Mahanagara Palike Mayor Sampath Raj also met the families of the deceased.
He expressed disappointment over the incident and said that despite so many equipment being available for the sewage treatment, people are still using labourers.(ANI)