New Delhi, April 16 : Safdarjung Enclave's B Block in the national capital has been declared a containment zone after four members of a family tested positive. The office of the District Magistrate (South) on Wednesday said the area will be made a containment zone. According to an official from the DM office, the B-Block of the Safdarjung enclave will be the new containment zone. As per the history of the patients, one patient was undergoing dialysis in a nearby hospital and was declared COVID positive on April 10 and admitted to RML hospital the same days. For the other family members, they were mostly staying at home during the lockdown and wearing masks while going out for groceries. The family members did not have any visitors and their contact history is being traced although they mostly stayed at home during the lockdown. There are already four containment zones in the South District. So far, Delhi has 57 containment zones across the city, with one new red zone being added on Wednesday in the North District. The 'G, H and I Blocks in Police Colony, Model Town, in the North District were made a containment zone on Wednesday, according to the Delhi government. While nine new containment zones were announced on Tuesday, four red zones were announced on Monday. Earlier, 10 new red zones were announced on Sunday. Containment zones, also known as red zones, are areas sealed by the district administration after at least three positive coronavirus cases surface from the locality. Among the districts, the highest containment zones are in the South-East District with 14 such zones, followed by the East District with nine red zones. After the administration seals an area naming it containment zone, the Delhi government starts 'Operation SHIELD' in the area. Operation SHIELD -- Sealing, Home Quarantine, Isolation and Tracking, Essential Supply, Local Sanitisation and Door-To-Door Checking -- is used to control the spread of the virus, according to the Delhi Health Department. Delhi has reported more than 1,550 COVID-19 cases and 30 deaths related to the dreaded virus so far. /IANS