Temporary structures for the new National Stadium set to serve as the main venue for the 2020 Tokyo Olympics and Paralympics are expected to cost more than double initial estimates, a source with the organizers said.

The overlay expenses that will come in addition to the costs for the main, permanent structure are likely to amount to about ¥10 billion ($87 million), while the anticipated spending in the bid was ¥3.8 billion, the source said Thursday.

The latest estimate includes costs to build a subtrack site that is needed as a practice area, and the source said that it is not yet clear whether the subtrack will be considered temporary.

“We are still discussing the matter with related organizations so we do not have accurate calculations,” the source said, adding that the final amount will “change significantly” depending on whether the subtrack area is seen as temporary or permanent.

Some in athletics circles want the subtrack to be permanent, saying it is necessary to continue holding international competitions at the stadium.

The fate of the National Stadium after the games has yet to be decided, with options being to use it exclusively for ball games, including soccer, or to also stage other athletics competitions there.

The central government, Tokyo Metropolitan Government and the organizing committee will discuss how to share the burden of costs for maintaining the temporary facilities, scheduled to be completed at the end of November 2019.

Main construction work for the stadium began last December in a contract worth about ¥149 billion.