A heavily overloaded boat packed with around 250 Iranians and Afghans seeking new lives in Australia sank off Indonesia, with bad weather and high seas hampering rescue efforts Sunday, officials said. The fibreglass vessel was following a well-worn, and occasionally disastrous, route from the southern coast of Java to the remote Australian territory of Christmas Island when it sank on Saturday, officials said. So far rescuers have plucked 33 people -- 30 men, a woman and two children -- from the sea despite strong currents and waves of up to five metres (16 feet), said a search and rescue official in Trenggalek district. "The survivors had been hanging on to six life vests and floating in the sea for around five hours before fishermen found and rescued them," the official, Kelik Purwanto, told AFP. The boat was carrying around 250 people when it sank 40 nautical miles off Prigi beach in the east of Java island on Saturday afternoon, he said. Thousands of asylum-seekers head through Southeast Asian countries on their way to Australia every year and many link up with people-smugglers in Indonesia for the dangerous sea voyage. Australia has warned refugees against attempting to come by boat, with officials often citing a December 2010 shipwreck at Christmas Island in which close to 50 people are believed to have died in wild seas. Purwanto said that around 60 rescue officials had been deployed to comb the sea to look for the passengers still missing from Saturday's disaster. Survivors said that they and the other passengers came from Iran and Afghanistan, and they had paid agents between $2,500 and $5,000 to seek asylum in Australia, according to Purwanto. "According to them, they had flown from Dubai to Jakarta and took buses to an unidentified location in Java to board the boat. They said they were heading to Christmas Island," he said. "They had been out at sea for 23 to 25 hours. They might have washed up on nearby islands, so we must try to rescue them as soon as possible," he added. Yoso Mihardi, a spokesman for the Trenggalek district government, said: "The boat had a capacity of 100, but it was overloaded with 250 people. "That, combined with heavy rain and high waves, might have caused the boat to tip over and capsize," he said. "Our focus now is on rescue efforts and also to ensure the survivors are recovering well and given adequate food, water and medical assistance," Mihardi said. The Indonesian government's immigration department would later take responsibility for the survivors, he added. Australia has failed in its efforts to set up a regional processing centre in neighbouring countries in an attempt to reduce the flow of asylum-seekers heading to its shores. Canberra had intended to deter people-smugglers by sending up to 800 asylum-seekers arriving by boat to Malaysia, in return for accepting 4,000 of Kuala Lumpur's registered refugees. But the proposal was scotched in August by the High Court which placed all offshore processing in doubt, and the conservative opposition has so far effectively blocked new legislation to allow it. More than 5,500 people are currently being held in either immigration detention centres or in community detention in Australia. But the number of boatpeople arriving ballooned to close to 900 in November, with at least nine ships arriving in Australian waters so far this month.