The three were quarantined in a college building in Chandel district after their return from Delhi.
They have now been shifted to the Jawaharlal Nehru Institute of Medical Sciences in Imphal, officials said.
The Chandel district administration has declared the college as a containment area, officials said.
The state which was declared COVID19-free on April 19 has 70 active cases now. Eleven patients have recovered.
The spurt in the number of COVID-19 cases was linked to the arrival of stranded Manipuris from different parts of the country. COR NN NN