The organizing committee of the 2020 Tokyo Olympics is considering reducing the capacity of the sailing competition venue from the initial 5,000 spectators due to the potential risk of tsunami, committee sources said Wednesday.

In addition to spectators, some 3,000 personnel associated with the sport are expected to go to the facility in Kanagawa Prefecture, southwest of Tokyo, but it is still not clear how to evacuate all the people including many foreigners in the event of a disaster, prompting the organizing committee and others to start studying measures to ensure safety.

According to the Kanagawa government's initial plan presented to the prefectural assembly, some 5,000 spectators will be seated on the breakwater on the east side of Enoshima Island.

But the organizers thought the road to high ground designated as an evacuation site in the event of tsunami is too narrow and too close to the coast so that people may not be able to evacuate safely, the sources said.

The committee is now contemplating a plan to cut the number of spectators to hundreds, the sources said, adding there was a call for hosting competitions with no spectators during discussions.

Tsunami hazard and evacuation maps created by the Fujisawa city government indicate that if a big earthquake occurs along the Sagami Trough running from Sagami Bay to the seafloor off the Boso Peninsula, nearly a 4-meter-high tsunami could reach around the competition venue after around eight minutes.

Other spots are designated as tsunami evacuation sites on the island, such as Enoshima shrine and a botanical garden, but the sites are about 700 meters away from the spectator seating, and evacuees need to overcome a difference of up to 60 meters in elevation.

The facility for sailing was initially planned to be built in Tokyo's Koto Ward but it was changed to Enoshima because the original venue was close to Haneda airport and helicopters covering competitions will be affected by flight restrictions.