Australian and Indonesian rescue workers are searching for for a missing boat, believed to be carrying scores of asylum seekers.Six people were rescued on Thursday morning, but more than 140 are still remaining missing.Al Jazeera’s Step Vaessen, reporting from Jakarta on Thursday, said: "Time is running out, as it has now been 38 hours since the whole incident began”A distress call on Wednesday said the boat had engine trouble, according to the Australian Maritime Safety Authority (AMSA)."The search and rescue operation will continue throughout the day with the focus on recovering survivors,” an AMSA statement said.This is the latest in a series created by a growing human-smuggling trade in which thousands of would-be refugees from countries including Afghanistan, Iran and Sri Lanka travel from Indonesia to Australia in overcrowded fishing boats.The crew of a merchant ship taking part in the search, Liberian-flagged APL Bahrain, spotted survivors in the water early on Thursday 75km southwest of Java and rescued six people. The Bahrain’s captain, Manuel Nistorescu, told the Fairfax Media website that he also saw what he believed were bodies in the water."I think I saw some of them dead,” he said.Nistorescu said the six rescued, all Afghan men, had been in the water for almost 24 hours.There were also women and children aboard the asylum-seeker boat when it sank, said Nistorescu.The number of missing people could not be confirmed, Jason Clare, Australia’s home affairs minister, said."We have grave fears for a lot more,” he said. ‘’Don’t underestimate how difficult this task is; don’t underestimate how big the sea that we’re searching is.”Asylum detentionJo Meehan, Australian Maritime Safety Authority spokeswoman, said another four merchant ships and an Australian military aircraft had joined the search-and-rescue operation.Two Indonesian government ships, an Australian navy patrol boat and two aircraft from Australia were to join the search later on Thursday.Richard Marles, Australia’s junior foreign minister, said the emergency highlighted the need for Australia to urgently establish detention camps in the Pacific island states of Papua New Guinea and Nauru to hold asylum seekers who reach Australia by boat.The government hopes to send the first asylum seekers to a tent camp on Nauru in September in a strategy to deter others from attempting the same boat journey.Asylum seekers often target Christmas Island, off Australia’s northwest coast, to get to the country. They make the journey from Indonesia in boats that are usually overloaded and poorly maintained.In August, 60 asylum seekers were reported missing off the Australian coast.In June, a boat with 200 asylum seekers sank near the island - 17 bodies were found and another 70 were feared dead after a three-day search.That was the second boat to sink in a week, reigniting the debate on asylum in parliament.