Construction has started on the largest station of an express line to connect Shanghai's Hongqiao and Pudong airports.

The Sanlin South Station in the Pudong New Area is being built some 42 meters beneath the ground, to be one of the deepest subway stations in the city upon completion.

Covering over 20,000 square meters, the station will have four underground levels serving two rails of the airport express line and a branch connecting to Shanghai South Railway Station, the construction company said on Friday.