Of the three, a 34-year-old male from Sriramnagar area arrived on December 11, while a 44-year-old male of Dharmanagar returned on December 17.
The flawed testing system at a time when the virus could have been slowed stopped scientists and officials from seeing how fast it was spreading.
The claims and allegations were refuted by Ghose who said he was informed that the swabs being referred to in the plea were unused or defective.
An individual undergoing a test might be infected or not and the outcome may also be positive or negative.
As many as 61,778 tests, including 26,080 RT-PCR -- the highest till date for the city -- and 35,698 rapid antigen tests, were conducted on Tuesday for the detection of COVID-19.
Many experts and government officials have warned that the chance of the virus spreading will be greater during the cold weather.
A research said that antigen tests require a relatively high viral load - about 1,000 times as much virus compared to the PCR test -- to detect an infection.
RT-PCR is considered the more accurate test for detecting Covid-19 in asymptomatic patients, while an RAT is useful for quick detection in symptomatic patients.
RT Lamp-based Tests will help reduce backlogs in testing patients for Covid-19 because the process can identify positive samples in 10 minutes, the company said.
The cases include traders, auto drivers and people working in various workshops and beauty parlours, among others.
District Medical Officer K S Shinu told TNIE that the main aim of the initiative is to increase the number of tests.
As per the government mandate, international passengers on arrival have to carry their RT-PCR negative report, conducted within 96 hours before departures from the origin country.
The free COVID-19 testing facilities have been started at 244 locations in the BMC-run hospitals and dispensaries in the city, the release said.
High level of comprehensive testing on a sustained basis has also resulted in bringing down the national positivity rate, it said.
The Left government came under flak from the Opposition claiming that it has been a dismal failure in combating the pandemic owing to initiating less number of Covid tests.