Help trickled in Thursday, three days after a magnitude-7.7 earthquake struck off Indonesia, triggering a tsunami that has killed at least 311 people and left more than 400 missing. An assessment team from the nonprofit group SurfAid International had reached the disaster zone, but the area's remoteness prevented further contact with headquarters in Sumatera Barat, Indonesia. SurfAid had shipped 1,000 shelter kits to victims, and is preparing to send more supplies once communication is established, spokeswoman Jossi Syahrial said Thursday. The group was trying to work with government officials to establish an information and coordination hub for all non-governmental organizations, she said. The hard-hit Mentawai Islands region is among Indonesia's myriad islands. It's very difficult to reach the region either by boat or road, said Andrew Judge, CEO of SurfAid. The trip takes at least 10 hours in good conditions, according to aid agencies. The Indonesian Red Cross also had sent at least two aid teams. One aid shipment included about 400 body bags. Urgent needs are expected to include clean water, food, blankets, clothing, medical attention, emergency shelter and hygiene kits, said Ita Balanda, a program manager for the World Vision aid organization in Padang, Indonesia. An estimated 7,900 households were affected, she said. The worst hit area is North and South Pagai Island.