Papua New Guinea, which is still recovering from a deadly earthquake last week, was hit by a powerful aftershock Wednesday that left an estimated 18 people dead or injured, adding to a mounting toll from the quakes, officials said.

The exact toll from the magnitude 6.7 aftershock that struck just after midnight was not immediately known, Papua New Guinea’s National Disaster Center said.

More than 100 people were killed in a magnitude 7.5 earthquake that struck on Feb. 26, said Uvenama Rova, secretary general of the Papua New Guinea Red Cross. That quake and subsequent aftershocks were centered in the country’s remote Highlands Region, and a complete picture of the scope of the destruction has been slow to emerge.

At least 67 people were killed in Hela Province in central Papua New Guinea, according to an estimate by the Hela Council of Churches. An additional 38 or 39 died in Southern Highlands Province, the Papua New Guinea Red Cross said.