One week after Papua New Guinea was rattled by a powerful earthquake, aftershocks have reportedly caused the death toll to rise to at least 67, while landslides have made the worst-hit highlands nearly unreachable.

Dozens of aftershocks have added to the devastation inflicted by the initial 7.5-magnitude quake last Monday. Three particularly strong aftershocks bigger than magnitude 5 hit the Southern Highlands early Monday morning, the Guardian reports.

All four regions struck by the quake remain under a state of emergency.

Aid workers told the Guardian that the extent of the damage is still unknown due to the remoteness of the villages bearing the brunt of the quake.

Thousands are thought to be trapped in isolated areas after landslides blocked roads to the worst-affected communities, making it all but impossible to deliver urgently needed supplies including food, water and healthcare.

“Many places that have been struck are still inaccessible, except by walking in, so there is a huge supply issue in delivering aid,” Udaya Regmi, the country head of the Red Cross, told the Guardian. Regmi estimated that at least 500 people are injured and 127,000 are in need of immediate assistance.

While earthquakes are a common occurrence in Papua New Guinea, which is located in the Pacific Ring of Fire where most of the world’s earthquake activity occurs, the latest tremors have been particularly catastrophic.

Local residents near the epicenter of the quake in Hela Province told Radio New Zealand that relief organizations have not yet reached them. One resident described immense devastation and said he was living on top of the rubble of his home with dwindling food supplies and contaminated water to drink.

In a statement, Darian Clark, the humanitarian duty officer at the Australian high commission in Papua New Guinea, said it “was the biggest earthquake in a hundred years and it spread 150 kilometers across the fault line.”