The Seoul city government conducted its own survey on soil and water near the US base in the central part of the capital for possible contamination with toxic chemicals on Wednesday, amid growing calls for the disclosure of pollution levels in the area.

Officials from the Seoul Metropolitan Government visited the outer areas of the US military base in Yongsan to examine the soil and groundwater, according to the city government.

They selected six spots outside the fenced-off military camps to extract soil and water from as deep as 10 meters down, it said, adding that it will take about a month to analyze it and reach a conclusion. 

It is the first time that the city government has carried out a test of its own to analyze the level of contamination near the US army base in Seoul. It had surveyed water near a subway station closest to the base, from which it claimed to have detected benzene 587 times the permissible level.

The latest survey, which began early this week, comes amid mounting calls for the public disclosure of the environmental state of the military base, as the US Forces Korea is relocating a large part of their troops to the city of Pyeongtaek.

The Ministry of Environment has conducted three separate tests inside the base in joint efforts with the USFK and it released the first lot after a Seoul court ruled in favor of a civic group which filed a suit demanding the public disclosure.

Separate litigations are under way between the ministry and the civic group over the release of the remaining environmental reports.

Advocates of the Seoul city's move have blasted the central government for not drawing up a clear plan with the US over the responsibility and expenses for purification, after the relocation is complete, if there is any contamination.

The ministry has insisted keeping the results "off-limits," citing the South Korea-US Status of Forces Agreement.

The Seoul city government says it has spent some 6.2 billion won ($5.45 million) of taxpayers’ money to clean up the groundwater near the Yongsan base since 2001. (Yonhap)