Police evacuated Grindavik in November after strong seismic activity in the area damaged homes and raised fears of an imminent eruption. Officials said magma could continue in that direction.
Mexico has deployed some 7,000 soldiers to the area of the volcano, which is near Mexico City, in case an evacuation becomes necessary. More than 25 million people live within 60 miles of the peak.
Two wharf workers tested positive Tuesday. The Ministry of Health has been testing workers there amid international aid shipments after last month's volcanic eruption.
A station to detect nuclear weapons tests picked up the volcanic eruption in Tonga from Antarctica. Some experts say the blast could be more than 50 megatons, while NASA estimates 6-10 megatons.
Authorities on the Canary Islands declared an eruption that started in September officially finished following 10 days of no lava flows, seismic activity or significant sulfur dioxide emissions.
Indonesia's geological agency said it sees increasing activity that could trigger an avalanche of lava and searing gas, similar to the Dec. 4 eruption,
The Cumbre Vieja volcano has damaged hundreds of homes and forced more than 6,000 people to evacuate as lava raced across La Palma, part of the Spanish archipelago known as the Canary Islands.
The volcano, which had not erupted in nearly two decades, caused thousands to flee, many across the border to Rwanda. But the lava didn't appear to be flowing toward Goma, a city of nearly 2 million.
St. Vincent's National Emergency Management Organization raised the island's alert to red on Thursday, after days of increased seismic activity at the La Soufriere volcano.
