Chennai, May 24 : Amid concerns over rising Covid-19 cases in the state, the Tamil Nadu health department has issued an alert to contain the spreading virus. On Tuesday, the number of fresh infections rose to 13, which was almost double the previous day's figure. While three persons in Chennai and two in Coimbatore tested positive for Covid-19, one each tested positive in Chengalpattu, Salem, the Nilgiris, Thoothukudi, Tirunelveli and Vellore as per the Directorate of Public Health , Tamil Nadu. Two persons who arrived at Chennai from UAE and Singapore also tested positive. The state public health department has directed the district health officers to tighten its vigil. However, 16 persons recovered from the disease on Tuesday and presently 89 are under treatment. No casualties were reported in the state due to Covid-19. State Health Minister, Ma Subramanian while speaking to IANS said, "There is no need to worry but we are being cautious. An alert has been issued to all the district health officers for any symptoms of the cases. We are well equipped." /IANS