Assessors from UK charity Oxfam have reported major damage on the Indonesian island of Nias following a massive earthquake which left hundreds dead.
People in the region have been leaving coastal areas
Items such as water tanks and fuel are due to be flown to Nias from Oxfam's Indonesia warehouse to help the effort.
The assessment team arrived on Tuesday by helicopter from Banda Aceh, where they have been working since the tsunami on 26 December 2004.
Aid worker Alessandra Villas-Boas said water supplies had totally collapsed.
In the town of Gunung Sitoli 20,000 people are without water and roads have been destroyed, making car travel impossible, she said.
"Huge holes have been made in the roads. Bodies are being pulled from the rubble as I speak.
"Unless we get a water supply back up and running, disease could break out and more lives could be lost.
The quake struck around midnight local time
"Tomorrow we'll begin to fly in emergency supplies so we can get clean water and basic supplies to people."
The team have ordered not only water tanks, but tap stands, generators to restart the local water system, fuel for generators and water trucks, 4,000 jerry cans and chlorine for water purification.
Other items due to arrive include tents, torches, cooking untensils and gloves, boots and masks for those gathering the bodies.
The town's water supplies have failed because the electricity grid collapsed in the earthquake, making the pumps which operate the system useless.
The Oxfam team, which includes an engineer and an emergency response specialist, has seen a mosque currently being used as a morgue for 34 bodies and as temporary shelter for displaced people.
They also say there are reports of food shortages.
British travellers in the region have been advised to stay alert after the quake, thought to have killed hundreds.
The earthquake happened just before midnight local time, affecting the island of Nias.
Tsunami alerts were issued in several countries, but later scaled back.
The Foreign Office advised Britons in south-east Asia to listen to media reports and take any precautions recommended by local authorities.
The earthquake had a magnitude of 8.7
A spokesman added: "Those intending to travel should check with their travel agents or tour operators before starting journeys to the affected countries."
After the quake Indonesia, Thailand, Sri Lanka, the Maldives, India, Malaysia and Mauritius had issued warnings of possible tsunamis, causing people to move away from the coast.
It is three months since the 26 December tsunami, which killed at least 300,000 people in 12 countries and caused major damage.
British Geological Survey seismologist Russ Evans told the BBC that Monday's earthquake was almost certainly an after-shock of the earlier quake, which had a magnitude of 9.
- Jakarta (Indonesia) (00) (62) 2131901314 or (00) (62) 811802435
- Phuket (Thailand) tel (00) (66) 76264473
- Colombo (Sri Lanka and The Maldives) tel (00) (9411) 2437336
- Mauritius tel (00) (230) 252 8006