SKOPJE, North Macedonia (AP) — A fire in a COVID-19 hospital in North Macedonia that killed 14 people last month was caused by the short-circuit of a cable connected to a defibrillator and spread fast due to the presence of stored oxygen for the patients, authorities said.

The public prosecutor's office said in a statement late Tuesday that the short-circuit occurred in a defibrillator used to resuscitate a patient in one of the rooms of the hospital in the northwestern town of Tetovo. The overheating cable set alight a junction box which the defibrillator, a mobile phone charger and another device were plugged into.

The prosecutor's office said medical staff attempted to extinguish the initial flames, but the blaze spread quickly to the roof panels of the field hospital and from there to the lower areas of the walls and to hospital equipment.

The temporary facility, which had been built amid a surge in coronavirus cases, was destroyed within minutes. Twelve patients and two visiting relatives died in the Sept. 8 blaze, and another 12 people were injured.

Health Minister Venko Filipce offered his resignation two days after the fire, as did his deputy minister and two senior hospital administrators. But Prime Minister Zoran Zaev said late Tuesday he decided not to accept the resignations.

“There is no reason to attribute political or managerial responsibility for Minister Venko Filipce and Deputy Minister Ilir Hasani, who resigned for moral reasons," Zaev said, adding that authorities would deliver their findings on potential mistakes made. He said he has “full confidence” that both have the capacity to continue running the country’s health system.

Zaev said the field hospitals were built under emergency conditions during the pandemic and were not intended to be equipped with oxygen as they were constructed to treat milder COVID-19 cases.

But a surge in infections led to a shortage of beds in state hospitals, and health authorities decided to allow the installation of oxygen systems vital for the care of seriously ill patients in the field hospitals, he said.

Zaev said he had ordered the health ministry to inspect all field hospitals in the country.

“The most important thing now is to strengthen the controls and checks in order to reduce the risk of such accidents,” Zaev said.

Nineteen field hospitals, funded by a World Bank loan, were set up across North Macedonia over the past year to tackle surging coronavirus hospitalizations and a shortage of hospital beds. Health authorities say all 19 were constructed according to the specifications and standards laid out by the World Bank as a condition for the loan.