TOKYO (Kyodo) -- Japan's weather agency said Wednesday that data from an offshore tsunami gauge in the Pacific Ocean is currently unavailable, raising concerns that observation could be delayed by up to seven minutes in the event of major earthquakes.

The system, located off the Tokai region along the Nankai Trough -- a zone feared to generate megaquakes -- is part of the country's tsunami monitoring network. The Japan Meteorological Agency said it is unclear when the system will be restored.

The Nankai Trough stretches southwest off the Pacific coast of central Japan. The government has urged municipalities in areas at risk of massive earthquakes and ensuing tsunami to conduct regular evacuation drills.

The agency said the failure of the system installed on the seabed will not affect the initial issuance of tsunami warnings or advisories, as they are based on estimates of an earthquake's magnitude and epicenter.

But it added that there may be delays in upgrading advisories to warnings depending on observed tsunami conditions. The system transmits data collected on the seafloor via cable to a land-based observation station in Shizuoka Prefecture.