Bhubaneswar: Thirty One students of National Institute of Science Education and Research, Bhubaneswar, have been tested positive for the Covid-19 infection. After conformation of the tests, the Khordha district administration has declared the vicinity as a containment zone. While the students have been isolated inside the hostel, contact tracing has been started and the premises will be sanitized. All the infected students are said to have mild symptoms and their health condition is stable.