New Delhi: Behind polite “namastes” and a high rent of Rs 15,000 — more than double what other tenants pay a month — a suspected synthetic drug lab used to operate out of a flat in a residential building in north Delhi’s Swaroop Nagar.Nearly three weeks after a Nigerian woman plunged to her death from the fourth-floor flat during a police raid on June 11, several residents of the building said they are connecting the dots only now.Giving the impression of an unusually secretive household, many of them told TOI that the inhabitants of the flat would often be seen flitting in and out of the building’s main gate between 1 am and 3 am, wearing fanny packs and carrying heavy bags. They allegedly bribed local sweepers with cans of Red Bull to help them carry blue plastic drums upstairs.Neighbours living downstairs spoke of a suffocating, urine-like stench of chemicals so overpowering that most avoided going upstairs, and mothers barred their children from playing on the roof of the building.The locality is now under the police scanner, with this incident coming barely two years after a blast in another meth lab run out of a house in the area led to the death of two Africans.Police unearthed the lab on the fourth floor while raiding it in connection with an NDPS (Narcotic Drugs and Psychotropic Substances Act) case. During the operation, Romeo, a Nigerian, was arrested with MDMA and heroin, while his compatriot, Stella Pius, jumped to her death from the balcony of her two-bedroom flat in a bid to evade the cops. Inside a room in the flat, lots of chemicals, beakers, pipes, sacks and weighing machines were found, police said.When TOI recently visited the building, two of its residents recalled separate incidents when some children went upstairs but were not allowed to peek inside Stella’s flat. In one instance, water from an overflowing terrace tank had flooded the staircase, but residents said the occupants of the flat refused to let anyone upstairs and spoke to them from behind their closed door. One of the neighbours whose 15-year-old son once helped the Nigerian woman carry heavy bags to the fourth floor said she immediately shut the door when the boy reached the floor, without allowing him even a peek inside.“They didn’t know much Hindi. They would just say ‘namaste’ to us while going up and down,” recalled Maya, 60, another neighbour. Beyond that, the Africans kept almost entirely to themselves.Their daily routine stood out for its oddity. According to the neighbours, they would frequently go out and return in the early hours of the morning. “They would carry huge bags all the time,” said Divya, a first-floor resident. Several others claimed that they had complained to the caretaker of the building about having to repeatedly open the main gate late at night. Another neighbour said, “It was only after the police raid that I came to know that the residents of the flat used AC coils to manufacture MDMA.”The building is located just metres from a govt school in a densely populated residential neighbourhood, with more apartment blocks behind it. Locals said it was only after the raid that they came to know that flammable chemicals had possibly been stored in the building, leaving many shaken over what could have happened. They also wondered why proper tenant verification had not been carried out before the fourth-floor flat was rented out.A woman who goes by the name of Komal told TOI that she had lived on the fourth floor for six months while her own house was being built, but the stench ultimately forced her to move out. She recalled meeting Stella just a day before her death. “Stella seemed rattled. When I asked her what happened, she just said, ‘money problem’,” Komal recalled. Loud arguments could frequently be heard from the flat in the days leading up to the raid, many of the neighbours said.