Four people tested positive for coronavirus in the district on Friday.
Civil Surgeon Dr Shyamol Krishna Hawlader said they sent 141 samples for coronavirus testing and received 92 reports, of which four were positive cases.
Meanwhile, altogether 314 people are in home quarantine as of Friday, he added.
Earlier on Thursday morning, the Sadar upazila was put under lockdown.
But the restrictions have had little to no effect as people in the municipality area were seen roaming around.
The Directorate General of Health Services (DGHS) on Thursday evening declared the entire country as 'vulnerable zone' to virus infection.
Bangladesh has so far reported 75 deaths and 1,838 coronavirus cases.
The global death toll from coronavirus reached 146,969 as of Friday.
There have been 2,185,744 confirmed cases around the world after the highly infectious disease was first reported in China in December last year, according to worldometer.
Of those infected, 1,485,452 are currently being treated with 56,601 being in serious or critical condition.
The World Health Organization declared the coronavirus crisis a pandemic on March 11.