SHANGHAI'S Metro is to undergo a major extension over the next two years, with two new lines built and three extensions added to existing routes.
This will increase the local subway network to 500 kilometers of track by 2012, a top official with the Shanghai transport authorities said.
Zhou Huai, deputy director of Shanghai Transport and Port Administration Bureau, said: "The subway's transit abilities will be increased with the new lines built."
At present, Shanghai has 11 lines of 420km of track - the longest in the world - carrying 1.9 billion passengers a year.
A new round of Metro construction is part of a government strategy to spend billions of yuan on transport links over the next five years.
The construction of Metro Lines 12, 13, one extension of Line 9 and two extensions to Line 11 will get under way soon, improving links between downtown traffic hubs and outlying districts, Zhou said.
A short section of Line 13 opened to World Expo visitors but closed after the event ended last October.
Line 9 is expected to stretch further south in Songjiang District and the Pudong New Area in the east. Line 11 will cross beneath the Huangpu River, extending to Pudong.
Traffic authorities also said that work on 22 subway stations has resumed in downtown area, following a break during the Expo when almost all downtown construction was halted.
Meanwhile, tightened security measures adopted during the Expo, such as X-ray scanning of passengers' luggage, will remain in place for the time being.
Scanning machines will be retained at stations and the number of security staff hired during the event is unlikely to be cut, Zhou said.
However, many passengers have claimed that inspections have become more lax since the conclusion of the Expo, saying that staff do not usually try to catch passengers who skip checks.
The bureau insists that staff still conduct checks on big bags and scan smaller ones randomly.
Discussions with police are ongoing about the long-term future of the scanning machines, officials said.