the 20th century. In 1955, the quarantine station housed residents of Lazarus Island, after a rare high tide destroyed their homes. In the mid 1970s, the rehabilitating drug addicts were temporarily moved out when eighty-four Vietnam War (1955–1975) refugees were settled on the island. The final batch of Vietnamese refugees departed for a permanent host country in late 1975. In 1998, there was a rise in arrests of illegal immigrants and overstayers after the 1997 Asian Financial Crisis, and the government was anticipating a mass of Indonesian refugees after the May 1998 riots of Indonesia. From January to July 1998, there was an increase of almost 2000 illegal immigrants and 1000 overstayers arrested compared to the whole of last year. However, this may be due to more police raids and patrols targeting illegal immigrants. By June, there were fears that the mainland prisons' capacity would be insufficient. Thus, the government began constructing a temporary Prison Detention Centre on St John's Island to house potential spill over illegal immigrants and drug addicts. However, the expected influx of Indonesian refugees did not occur, and the temporary detention centre stands abandoned. Holiday camp and aquaculture research centres In the mid 1970s, the Sentosa Development Corporation planned to redevelop Singapore’s offshore islands into resort centres. However, proposals to redevelop St John's as a holiday island with restaurants, golf courses and an integrated resort-casino fell through. Instead, the 3 million dollar budget was spent on developing a holiday camp on the island with sports and games facilities. A three-day outdoor activities camp for schools was established on the island in 1975. St John's Island is currently the site of several aquaculture research and development facilities. The Marine Aquaculture Centre (MAC) is a hatchery completed in June 2003, and the National Marine Laboratory was established in 2002. In April 2018, traces of asbestos was found in construction debris around the island's campsite, lagoon and holiday bungalow areas. The two long-term residents on the island were evacuated and were assessed to be healthy. Access to the island was restricted while the contaminated debris was being removed. Geography St John's Island has a land area of and is located in the Strait of Singapore, about 6.5km from the southern coast of mainland Singapore. Its location is at longitude 1°13′08.30″N and latitude 103°50′53.88″E. All the Southern Islands, including St John’s, are formed by the Triassic rocks of the Jurong