With no fresh case reported overthe past three weeks, a slum cluster in Belgachhia area of north Kolkata, once marked as a COVID-19 hotspot, has been declared a green zone, an official here said on Monday.The congested slum belt, spanning two sq km, has become a role model for the rest of the city with its successful implementation of lockdown norms, he said.Swapan Samaddar, a member of the Board of Administrators at Kolkata Municipal Corporation, told PTI, that the bustee -- home to 3,0000 people - was taken off the list of containment zones last week, and the authorities declared it a green zone on Sunday."As no fresh cases were reported in the past three weeks, the slum, which had recorded seven to eight coronavirus cases including two deaths in April, has zero cases now. We will implement the Belgachhia model in other congested containment zones like Topsia," Samaddar said.After the slum was declared a coronavirus hotspot on April 14, as several cases tumbled out of the area, all lanes leading to the bustee were barricaded and police pickets set up to regulate movements.Residents were asked to stay at home and local clerics roped in to convince people to follow the safety norms.The KMC official thanked the local clubs, voluntary organisations and religious leaders in the area, for their concerted efforts to stem the spread of the disease."The shutdown was enforced in the slum in letter and spirit. From barricading entry points to spraying of disinfectants and home delivery of essentials, all possible steps were taken to control the spread. Shortly after, the number of cases decreased in the locality," he said.Samaddar noted that stand alone shops apart from grocery stores will be allowed to resume business in the area during the day time."Police and KMC personnel, however, will not lower the guards and random tests would continue. The local clinic will monitor the health of residents from time to time," he said.The KMC official expressed confidence that congested slums in Topsia, Rajabazar, Metiabruz and Dhakuria areas will also be declared green zones in the coming days, after the Belgachhia model is implemented in these places.