The island city of Xiamen in east China's Fujian Province has started building its first subway line, local authorities announced Wednesday.

The 30.3-km Line 1 will run south-north across the Xiamen Island and span the sea via elevated rails to connect with the city's northern part on the mainland, according to the city's office on subway construction.

The line is expected to start service in 2017, with a total travel time of 50 minutes, the office said.

Data show a total of 16 cities on the Chinese mainland have urban rail transit systems as of June, with a total track length of 2,037 km, a figure that will increased to 3,000 km in 2015.