SKOPJE, North Macedonia (AP) — Three women and a 10-year-old boy remain in critical condition in North Macedonia, a day after a home cooking-gas explosion that killed another four members of their extended family, health authorities said Monday.

The head of the intensive care unit in the capital Skopje’s hospital, Ilir Hasani ,said the women, aged between 30 and 50, suffered burns on 80% of their bodies and have been put on respiratory machines. The boy has burns on 75% of his body, Hasani said.

Two sisters aged 9 and 11 and their cousin, an 8-year-old boy, were killed instantly early Sunday when the gas cylinder exploded in the living room of a family house in the village of Romanovce. A 58-year-old man died of his injuries later Sunday in a Skopje hospital.

The village is near the northern town of Kumanovo, about 50 kilometers north from Skopje.

Ten people, all members of the same family including some who were visiting, were in the house at the time of the accident.

Apart from the three women and the child in critical condition, the remaining two people who were in the house — a 7-month-pregnant woman and a 65-year-old man — suffered lighter injuries.

It was unclear what caused the accident. Local media reported that the gas cylinder exploded while the family was preparing breakfast.

Kumanovo authorities have declared a day of mourning on Tuesday.