SHANGHAI: The cost of extending the city's maglev railway could be twice the original budget due to proposed revisions to minimize the impact on local residents, a source said yesterday.

A revised plan of the proposed route, published on the website of the city's urban planning administrative bureau, shows the line connecting Longyang Road with Hongqiao Airport, while avoiding densely populated areas.

Residents had earlier expressed concern about the possible health threat from magnetic fields around the railway.

The source told China Daily that costs could jump from 200 million ($27.5 million) to 500 million yuan for each kilometer of the extended line.

This is because a wider buffer zone between residents and the line has been proposed.

The government is yet to approve any extra funding.

There are also plans to extend the maglev line to the resort city of Hangzhou in Zhejiang Province.

The National Development and Reform Commission, is working to establish a company to head the project, the source said.

The Ministry of Railways and the Shanghai municipal government will each finance 40 percent of the total investment - which the source declined to disclose - for the Shanghai-Hangzhou maglev.

Zhejiang will finance the remainder.

Under the revised proposal, the Shanghai extension will stretch 31.8 km, 3 km less than originally planned, with significant "detours" away from residential areas. The changes were made because of residents' fears about perceived exposure to radiation and noise, the source said.

In response, authorities last year carried out environmental impact studies.

The revised route will be open for public comment for the next two weeks.

"Experiments have shown that the electromagnetic radiation is minimal compared with what is emitted from electronics appliances in the home," the source said.

"But the noise is a problem."

The Shanghai government is unlikely to abandon plans for the extended line, because 10 billion yuan has already been invested in the project, the source said.