Delhi: The Indore district administration on Friday invoked the National Security Act against four men involved in the alleged attack on health workers in Taatpatti Bakhal area of the city. This is first such action related to Covid-19 pandemic in Madhya Pradesh, an official said. A five-member team from the health department had gone to Taatpatti Bakhal on Wednesday to quarantine relatives and acquaintances of a Covid-19 patient, when an unruly mob attacked them with stones, injuring two women doctors. The police had arrested seven persons for the alleged attack on Thursday and the district administration has slapped the NSA on four of them, the official said. The Indore police on Friday detained six more men in connection with the incident. Six more men are being questioned about their involvement in the incident, Indore’s Chhatripura police station in-charge Karan Singh Shaktawat said.