New Delhi, June 2 -- "Zaildar Estate Private Road. Trespassers will be prosecuted," reads a black signboard at the entrance of the street in Saidulajab where a building collapse killed six people on Saturday evening. The so-called "estate" is owned by three brothers including 71-year-old Karamveer Zaildar, a resident of Church Road in Vasant Kunj, who was arrested by Delhi Police on Monday after a nearly 48-hour search in connection with the collapse. The building, where two additional floors were allegedly being constructed atop an existing four-storey structure, was identified by local residents as Zaildar's property soon after the collapse. However, investigators said police were able to establish the ownership trail only after obtaining documents on Sunday. Zaildar's name appears on lease agreements executed with tenants operating a co-working space and a media firm from the building. Police said the investigation revealed that Zaildar and his family own multiple land parcels in Saidulajab and along the same street. "It has emerged that the coaching centre adjacent to the collapsed building also belongs to the Zaildar family," an officer said. Records examined so far indicate the property was registered in the name of Zaildar's father, Mangal Singh, as recently as 2020. "We are yet to obtain all ownership documents from Karamveer, but the lease documents available with us carry his name," the officer added. Police also noted court cases involving some land parcels owned by Mangal Singh, adding that "those matters are sub-judice and not part of present probe." The probe has revealed that authorities had been alerted about construction activity at the site months before the collapse. A letter sent by Delhi Police in March to the Municipal Corporation of Delhi, reviewed by HT, flagged construction of the fifth floor at the property at Khasra No. 261, Lane No. 5, Westend Marg, and sought verification of if construction was being carried out as per sanctioned plans. "Please verify... whether the construction is as per sanctioned plan or otherwise. Necessary police aid will be provided," the station house officer of Mehrauli police station wrote....