The World Health Organisation has said there have been outbreaks of diarrhoeal diseases in settlements of displaced people in Sri Lanka.
150 cases were reported in one district there.
Dr Maura Connolly, the WHO's Head of Communicable Diseases in Complex Emergencies, said that WHO teams are sending samples to laboratories for testing.
Dr Connolly said the tests were to ascertain whether those affected are suffering from cholera, dysentery or typhoid.
Earlier today, the US Secretary of State, Colin Powell, said he cannot compare the devastation in Indonesia to anything else he has experienced.
Mr Powell made his comments on a visit to inspect the damage caused in the province of Aceh, the area worst hit by the tsunamis.
'The power of the wave to destory bridges, to destory factories, to destroy homes, to destroy crops, to destroy everything in its path is amazing', Mr Powell told reporters.
He said the US, which has already pledged $350 million in aid and has mobilised a big military operation, would step up its assistance.
Mr Powell has now travelled to the Indonesian capital, Jakarta, for tomorrow's emergency summit at which leaders of the worst affected countries and aid donors will discuss relief and reconstruction plans for the region.
The United Nations Secretary General, Kofi Annan, and the EU Commission President, Jose Manuel Barroso, will also attend.
The disaster has left about 150,000 people dead, with Indonesia, India, Sri Lanka and Thailand hardest hit.
