Nearly 1,300 people at a military academy in Indonesia have tested positive for the COVID-19 pandemic, an official said.

The Indonesian Army Officer Candidate School in the country’s most populated province of West Java has been quarantined and 30 people were initially hospitalized with mild symptoms, the army’s chief of staff, General Andika Perkasa, said late Saturday.

Of the 1,280 confirmed infections, 991 were cadets and the rest were staff and their family members, he said. Most had no symptoms, AFP reported.

Indonesian peacekeeping forces personnel march in a parade during the celebrations for the 74th Indonesian National Armed Forces day at Halim Perdanakusuma airbase in Jakarta, Indonesia, October 5, 2019. Reuters//Willy Kurniawan

The outbreak was first detected when two cadets went to a medical facility after complaining of fever and back pain. Both tested positive for COVID-19, sparking mass swab testing at the academy, which has 2,000 staff and cadets.

It is not clear how the cadets were infected, Perkasa said, but some staff live outside the military complex. It is the hardest hit country in Southeast Asia with more than 74,000 known cases of COVID-19 and over 3,500 deaths.

The real toll is widely believed to be much higher, however, with experts saying limited testing was understating the true scale of the crisis.