Two of the four apartment complexes found to have violated Coastal Regulation Zone norms were reduced to debris within seconds of controlled implosions that brought them down in Kochi on Saturday.

Watched by thousands of onlookers who had arrived from across Kerala, the high-rises were brought down like a pack of cards, kicking up a thick cloud of toxic dust over the Maradu neighbourhood, including the picturesque Vembanad Lake.

The buildings that were 19 floors high each were demolished based on a Supreme Court order in May 2019 that cited violation of CRZ norms since none of them had maintained the necessary distance from the lake.

While Holy Faith H20 was the first to be imploded at 11.18am, the two towers of Alpha Serene apartment complex were reduced to debris minutes later.

The remaining two apartment complexes would be demolished on Sunday by using the same controlled implosion technique. This would reduce the five towers of the four high-rise complexes that house 500 flats to 70,000 tonnes of debris.

The three towers were brought down on Saturday in such a controlled manner that even the gates of Holy Faith H20 were left intact.

While Holy Faith H20 had just one tower, Alpha Serene had two adjacent towers, both part of the same project.

Alpha 1 crashed within the defined parameters, but some debris from Alpha 2 crashed into the lake.

Ernakulam collector S. Suhas later clarified that was part of the plan to save a nearby house.

“The debris of all the buildings fell inside their compounds. Even Alpha 1 was contained inside the compound. Only some debris of Alpha 2 fell in the water, which was deliberately done to save a house that stood just metres away. All vibration readings are within safety limits,” he told reporters at the site.

The apartment Holy Faith H20 implodes in Kochi, Kerala, on Saturday (AP photo)

Ernakulam city police commissioner Vijay Sakhare said the buildings were demolished as planned.

“The buildings have been demolished as planned by explosion experts. The collateral damage is absolutely nothing. There was no harm to human or animal life,” Sakhare told reporters.

The police had evacuated all residents from a 200-metre radius where several houses were located.

A relieved Utkarsh Mehta, managing director of the Mumbai-based Edifice Engineering that brought the towers down, confirmed there was no collateral damage.

“All debris fell within the boundary limit and there was no damage to any house. We have checked all the houses and all of them are safe,” Mehta said about an hour after the operation.

Thousands of people from across the state had gathered to watch the buildings being brought down through controlled explosions.

The police had cleared all roads within a 200-metre radius and the Kundanoor Bridge, a major cause of anxiety as the towers were a short distance away.

But to the relief of the authorities, there was nothing untoward except for a thick cloud of smoke that covered half of the bridge for a few minutes after the explosion.

Several people staged a protest as the roads were blocked for longer than the promised 30 minutes since post-demolition checks were still on.

The state government had dithered when the Supreme Court ordered that the residents be shifted by May 20. The apex court then set a revised deadline to complete the evacuation and demolition before September 20.

Although the residents had put up a massive resistance, all facilities were eventually disconnected on September 26, leaving them with no option but to move out.

Police had meanwhile booked the builders for breach of trust and cheating.

The final act of demolition got pushed to January 2020 because of the extensive process of preparing the buildings for the implosions.

Once the whole operation is over on Sunday, the Maradu neighbourhood, known for its luxury apartments that offer some of the best waterfront views in the state, would have five huge mounds of debris, each of them the height of a four-storey building.

Prompt Enterprises, based in Kerala, has been given the job of clearing the debris within 70 days from Sunday. The hundreds of truckloads of concrete debris and shattered cement blocks would be taken to yards Aroor and Chandiroor in Alappuzha where they would be processed.

The end products of the debris from some of the most sought-after apartment complexes in Maradu would be paving tiles, m-sand (an alternative for scarce river sand) and hollow bricks.