An Indonesian official has revealed significant holes in the tsunami warning system around the Mentawai Islands in Sumatra.
More than 400 people are dead and at least 300 missing after a magnitude 7.7 earthquake triggered a tsunami which swept villages away in the remote island chain on Monday.
On 26 December 2004, a tsunami caused by a 9.1 quake off the coast of Sumatra killed more than 226,000 people in 13 countries. It was the deadliest tsunami on record.
Following that tragedy, a string of sensor buoys was distributed off the Indonesian coast, the ABC reports.
However, the deputy chairman of the agency responsible for managing the buoys, Riduan Jamaluddin, says most of them are not working and initial plans for 22 were scaled down to 12.
In the wake of the tsunami which struck the Mentawai Islands, he has revealed that only three or four have survived technical problems and vandalism.
While the buoys are not critical to monitoring the Indian Ocean, gaps in the chain will cause a delay in alerts about future tsunamis.
System failed for quake close to coast
Indonesian foreign ministry official Kusuma Habir told the BBC the earthquake that caused the tsunami was too close to land for the early warning system to be of any use.
Ms Habir says the wave hit the coastline faster than the hour it takes to send a signal. The tremor was centred 80km out to sea.
She said Indonesia is setting up equipment to detect an earthquake and tsunamis near the coast and sirens will also be installed.