Chennai: Two men including a guest worker who worked on the water at the location under construction in Choolaimedu died of shortness of breath on Monday, police said.
The deceased was identified as Muthukrishnan, 40, Thiruverkadu, and Sultan, 25, a guest worker from Kolkata.
The police said Balu, 59, a retired Tangedco staff, has built a 900-set house by involving a contractor named Raj Babu, in Koreatur, in Namachivayapuram in Choolaimedu.
Muthukrishnan, who worked for Raj Babu, had built a bah three months ago and was closed with a concrete slab when the job was jammed because of Covid-19.
When it began to be filled with rainwater after a recent bath, Muthukrishnan visited the site with the Sultan helper on Monday to remove the scaffold placed inside and finish the work.
Both entered bah after removing the top of the concrete but immediately Mutathukrishnan fell into the water and became unresponsive.
The Sultan tried to save him and faint too.
One worker on the site saw this and warned fire service personnel and rescue.
The police also arrived at the place.
Rescue personnel entered the protective equipment and issued a duo in an unconscious state.
They rushed to the Kilpatuk Medical College (KMC) hospital where the doctor said they were taken dead.
Police said Gas Noxious had filled the room because it was still closed for months.
Police Choolaimedu has registered a case and further investigation.