Authorities in Indonesia are preparing to send emergency teams to douse forest and bush fires causing thick smog in Sumatra's Riau province, an official said Friday. Haze has blanketed parts of Riau on eastern Sumatra island in recent days and satellite images showed 366 hotspots indicating fires in nine districts on Wednesday, dpa quoted the National Disaster Management Agency as saying. "We need to put out the fires as early as possible before they spread further," said Saqlul Amri, the head of the Riau Disaster Management Agency. Several helicopters were being prepared to drop water on the fires, he said. In March, haze from forest fires forced the closure of Riau's international airport for several days and caused respiratory problems in an estimated 60,000 people. Haze in Sumatra is an annual hazard during the dry season - which begins around May-June - and often affects neighboring Malaysia, Singapore and Thailand.