The five persons - four jawans and a cook are posted at the BSF camp in Vanhne in south Mizoram's Lunglei district.
The four jawans recently returned to the state from Kerala, Madhya Pradesh, Assam and Meghalaya and were under quarantine, while the cook has no travel history, the official said.
The five, who are aged between 27 and 52 years, are asymptomatic and out of danger, he said.
A total of seven personnel of Vanhne camp are now afflicted with the disease.
Mizoram now has 58 active cases while 133 patients have recovered from COVID-19.
According to the health department, Lunglei district accounted for the highest number of 54 cases, followed by Aizawl with 53. The remaining 84 cases were reported from eight other districts. Only Hnahthial district is still COVID-19 free.
All the coronavirus infected patients of Kolasib, Serchhip, Khawzawl and Saitual districts have already recovered. COR NN NN