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.
The images show populated areas in the archipelago with heavily damaged or destroyed buildings and homes and at least one island covered with ash.
A second, domestic fiber-optic cable that connects Tonga's smaller islands to the main island could prove much more difficult to repair.
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.
Researchers who have been studying the volcano since 2015 say it was likely caused by seawater flowing into a chamber filled with magma.
Ecuador's Emergency Operations Committee said the eruption on Isabela Island didn't represent a risk to humans or to native local species.
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.