Two residential towers taller than the Qutb Minar collapsed in a volcanic eruption of dust in Noida on Sunday when controlled explosions brought them down on the orders of the Supreme Court for violation of building rules.

The twin towers — Apex (32 storeys) and Ceyane (29 storeys) — were built by real estate developer Supertech with the active support of the Noida Authority. The original sanction was for nine floors, which was gradually increased to 40. The builder was supposed to leave a distance of more that 40 metres between the two towers, but Supertech left a gap of only nine metres.

Over 3,500kg of explosives were used to demolish the two towers that reached up to 94 metres and 103 metres, the tallest structures ever pulled down in the country.

From rooftops of buildings, people watch the demolition in Noida on Sunday. PTI picture

Officials estimated the quantity of the rubble at 60,000 tonnes, including 40,000 tonnes of steel. Others put the figure at 80,000 tonnes, saying most of the rubble will be used to fill the site and the rest will be recycled.

Over 1,200 trucks will take 90 days to clean the spot, the officials said.

“It took 12 minutes for the dust to settle but we will keep monitoring the air pollution because of the possible presence of some dust particles in the atmosphere for about two months,” Noida district magistrate Suhas L.Y. said.

Around 400 metres around the site in Sector-93A was cordoned off and residents of the adjoining areas were evacuated two days ago. Four anti-smog guns started sprinkling water seconds before the demolition that was remote-controlled from around 50 metres.

A sequence of images depicting the demolition of Supertech’s twin towers in Noida on Sunday. Over 3,500kg of explosives were used to bring down the structures in keeping with a Supreme Court order that held that the buildings were constructed in violation of norms. PTI pictures

Four hospitals were kept vacant exclusively for those who could have been affected. However, there was no report of any untoward incident.

Sudeep Roy, owner of a four-room apartment in a nearby low-rise building, said he booked hotel rooms last week to spend the night with family and friends.

“It is best to stay away from the blast site for 24 hours because the air will get toxic and we don’t know how it can impact our health,” said Roy, a mechanical engineer and father of twin boys, one of whom suffers from asthma.

All roads, including Noida Expressway, were blocked and traffic was diverted from 2pm to 4pm.

Crowds watching the collapse from rooftops on nearby high-rise buildings cheered and clapped as the towers fell.

Government sources said around Rs 17 crore was spent on bringing down the towers.

Uttar Pradesh deputy chief minister Keshav Prasad Maurya said in Lucknow: “These two towers were developed at the cost of Rs 400 crore without following building rules. The builder constructed triple of the approved number the floors and didn’t leave enough space between the two towers. About 30 employees, officers and contractors of Noida Authority and other organisations have already been booked and suspended for their involvement in this corruption, which was committed during Akhilesh Yadav’s rule between 2012 and 2017.”

Samajwadi Party leader Anurag Bhadauriya said: “Those who are corrupt believe everybody is corrupt.”

Allahabad High Court had in 2014 ruled that the towers were illegal and ordered their demolition. Supertech approached the Supreme Court challenging this order. The Supreme Court on August 31, 2021, upheld the high court’s verdict and said Supertech had violated building norms and pointed at “collusion” with Noida district officials. It held that illegal construction had to be dealt with strictly to ensure compliance with the rule of law.

“The case has revealed a nefarious complicity of the planning authority in the violation by the developer of the provisions of law,” the top court had observed.

The Noida Authority had given land to Supertech in 2004 and the plan was approved in 2005. In 2006, Supertech sought more land and got approval.

Awanish Awasthi, additional chief secretary (home), told reporters in Lucknow that the expertise of an African firm was taken to conduct this exercise.

An environment expert told this newspaper that the wind was blowing towards Aligarh, Agra and Mathura during the demolition. “Delhi was protected naturally but west Uttar Pradesh would be affected for many days. We have reports that the sound of blast was heard 10km away and glass windows and doors of over 50 houses developed cracks,” he added.

Additional reporting from Reuters