A strong aftershock shook the traumatized Indonesian island of Lombok on Thursday as the death toll from a major quake earlier this week pushed past 250 and aid groups struggled to help tens of thousands of people left homeless.

The latest temblor sent panicked residents into the streets as more buildings collapsed.

The aftershock — the third since Sunday’s quake — had a magnitude of 6.2, according to Indonesia’s geological agency. It did not have the potential to cause a tsunami, the agency said. The U.S. Geological Survey measured the quake at 5.9. 

The official death toll on Lombok stood at 259, according to a tweet by Sutopo Purwo Nugroho, spokesman for Indonesia’s disaster mitigation agency. He noted, however, that the count could rise.

Aid agencies also say the number is likely to increase as they gain access to the worst-hit parts of the island, which lies east of Bali.

Humanitarian groups say that they are focusing their efforts on reaching areas that have been impassable because of collapsed buildings and roads and other destruction after Sunday’s quake. 

“Access is tough, because the earthquake [on Sunday] was so strong and paralyzed a lot of buildings,” said Husni, a spokesman for the International Federation of Red Cross and Red Crescent Societies, who, like many Indonesians, goes by one name.

Speaking to The Washington Post by phone en route to a badly damaged village, he said almost 80 percent of the buildings, including homes, schools and community facilities, were destroyed in that area. Some villages have collapsed entirely.

Several bridges have been destroyed and landslides have hit, making aid support from the government and international nongovernmental organizations very challenging. 

“So far, we have been unable to pass through those areas. We are still working on it,” Husni added.

Witnesses described scenes of fresh panic Thursday afternoon as the new tremors hit. Displaced residents living in shelters rushed out of their temporary homes, fearing more destruction to structures weakened by previous quakes. 

One aid agency, Yayasan Plan International Indonesia, has warned that thousands of children have been left homeless, forced to sleep in open fields without warm clothing or blankets. More than 1,000 schools have been damaged, the agency said. 

“The shelters people have made for themselves are not safe or secure. Overnight, the children are cold. They don’t have blankets or proper clothing to keep warm,” said Hana Yulia, an emergency response worker. “A lot of children have developed colds, so they are suffering.”