Government approvals were granted for construction of the Island line in December 1980. Construction commenced in October 1981. On 31 May 1985, the Island line was opened with service between Admiralty station and Chai Wan station. Both Admiralty and Central stations became interchange stations with the Tsuen Wan line. Furthermore, each train was extended to eight cars. On 23 May 1986, the Island line was extended to Sheung Wan station. Construction was delayed for one year, as government offices which were located over the station had to be moved before the construction could start.