WELLINGTON—New Zealand's Ministry of Civil Defense canceled its potential threat advisory issued for the central North Island after Mount Tongariro erupted late Monday for the first time in more than 100 years, but said there is still an elevated level of risk.

Government-owned research institute GNS Science, which said the eruption occurred at 11:50 p.m. local time, issued a Volcanic Alert Bulletin due to potential disruptions from the ash plume. Late Tuesday it downgraded the Aviation Color Code to orange from red as the ash began to dissipate. Orange indicates heightened unrest.

"The latest assessment from GNS Science is that eruption activity has subsided...There is no ash being produced from the volcano presently. There have been no lahars or pyroclastic flows or lava flows," the civil defense ministry said in a statement.

It underscored, however, that as with any volcano, an eruption could occur at Tongariro at any time with little or no warning and there is an elevated level of risk, particularly on the northern slopes and valleys of the mountain.

Mount Tongariro is well known for the Mount Tongariro Alpine crossing, a 19.4-kilometer journey that traverses terrain formed by volcanic activity. The area is also the site of some of the filming in Peter Jackson's "Lord of the Rings" movie trilogy.