A portion of a housing society's boundary wall collapsed here on Tuesday morning, killing four construction workers and injuring eight, police said.
All 12 who had been buried under the rubble while repairing a drain adjoining it at the Jal Vayu Vihar in Sector 21 around 10 am were labourers, they said.
A team of Sector 20 police station later detained a sub-contractor, Gul Mohammad, who supplied labourers for the job, an official said.
Multiple JCBs were deployed to clear the debris of the collapsed stretch of the wall that was located adjacent to a drain, officials said as police and fire department personnel swung into action for immediate rescue and relief measures.
"A total of 12 labourers were pulled out of the rubble. Four of them died while others suffered injuries in the episode," Additional Deputy Commissioner of Police (Noida) Ashutosh Dwivedi told PTI.
The deceased have been identified as Pushpendra Singh (25), Panna Lal (25) and Amit (18), all from Budaun district in Uttar Pradesh, and Dharam Veer from Sambhal district, police said.
The injured was identified as Pappu Singh (25) of Budaun. He is undergoing treatment at the district hospital, they added.
Uttar Pradesh Chief Minister Yogi Adityanath condoled the loss of lives in the incident, his office said.
"Uttar Pradesh Chief Minister Yogi Adityanath expressed grief over the loss of lives in the wall collapse incident in Gautam Budh Nagar. He directed senior officials to rush to the spot and conduct relief work on a war footing," the Chief Minister's Office said in a tweet in Hindi.
He also directed the officials to ensure proper treatment of the injured, it said.
Police Commissioner Alok Singh, Joint Commissioner Love Kumar and Noida Authority CEO Ritu Maheshwari reached the spot. Fire service officials, including its chief Arun Kumar Singh, are also there to oversee the relief work, the officials said.
Maheshwari said repair work was being carried out on the drain when the accident occurred.
"The Jal Vayu Vihar society is an old-construction society. The boundary wall was also constructed by the society itself and looked weak," she said.
The work on the drain outside the society was being carried out on its request by a Noida Authority contractor through a tender, she said.
"The labourers repairing the drain came under the wall which suddenly collapsed. There were 12-13 people at the spot. Of those rescued, one is injured and the remaining are fine," Maheshwari said.
On the contractor being cautioned by locals that the boundary wall was weak, the Noida Authority CEO said the matter will be investigated.
"A joint investigation by police, district administration and Noida Authority will be carried out and if negligence is found on anyone's part then action will be taken against them.
"The contractor was working on the drain and not the boundary wall," she said.