A total of 181 students and staff at a private boarding school in the Nigerian capital Lagos have tested positive for coronavirus, state health authorities said on Friday.

Authorities said there had been a "minor but significant" outbreak among the 441 staff and students at the school in the suburb of Lekki and said most of the now-quarantined positive cases were asymptomatic.

Lagos state Commissioner for Health Akin Abayomi said in a statement posted on Twitter that the cases came to light after a 14-year-old girl fell sick on Oct. 3. She tested positive for Covid-19 on Oct. 6, prompting state health authorities to launch an investigation.

"Positive students and staff have been isolated on the premises ... and are being monitored in isolation within the school premises," Abayomi said.

He said authorities had taken steps to contain the spread of the virus, and were discouraging any students from going home, lest they infect family members.

Nigeria has confirmed a total 60,982 cases of Covid-19 and 1,116 deaths linked to the disease.

The government announced early this month that federal government schools could reopen from Oct. 12, while schools run by states and private owners could open on their own timetables, following a steady decline in the rate of infections in Nigeria.