Guwahati/Imphal/Agartala, With 187 new patients detected on Monday, the single biggest jump in 24 hours, the number of Covid-19 positive cases in Assam mounted to 539, while after Sikkim, Nagaland reported its first coronavirus cases when three people, who returned from Chennai, testing positive.

According to Assam Health Minister Himanta Biswa Sarma and health officials of other northeastern states, the return of 80,000 people from southern and western India back to the northeast has led to a steep rise in Covid-19 positive cases in the region, especially in Assam and Manipur.

Sarma, in a series of tweets, said 90 per cent of the 539 Covid-19 patients in the state have been reported from the quarantine centres across the state's 33 districts. Of the 539 positive cases, 470 are active cases and 62 discharged from the hospital and four died and three migrated to other states.

Meanwhile, with the resumption of operations of domestic passenger services after two months, several thousand people returned to Assam and Manipur on Monday.

According to the Airport Authority of India (AAI) officials, eight flights arrived at the Lokpriya Gopinath Bordoloi International Airport in Guwahati from Delhi, Bengaluru, Mumbai, Chennai and Imphal and these eight aircrafts departed with passengers subsequently.

According to AAI Regional Executive Director (NER) except Guwahati and Imphal airports, no passenger flight landed at any other airport in the northeastern states on Monday as the Kolkata airport, hit by the cyclone Amphan last week, was shut till May 27.

Besides Assam, the coronavirus infection increased in Manipur, which registered 34 new cases (all returned to the state from other states) in the past two weeks.

The northeastern state had last month been officially declared as corona free state after its two patients recovered from the dreaded virus.

In Tripura, with the four people, who recently came from Maharashtra, tested positive on Monday night, took the state's total Covid-19 positive cases to 198, including 161 Border Security Force personnel and their kin, with active cases count of 31.

Meanwhile, the three-member central team, led by G.K. Medhi, Professor and Head of the Department of Community Medicine of the Shillong-based North Eastern Indira Gandhi Regional Institute of Health & Medical Sciences (NEIGRIHMS), after 11-day visit and studying the source and other aspects of the coronavirus infection among BSF troopers in Tripura, submitted their report to the state government.