(CNN) -- One day after raising the alarm about a possible major eruption, authorities have lowered the alert level in and around a remote Alaska volcano.
A yellow alert -- the second most serious out of four possible levels -- has been issued for the Cleveland Volcano, the U.S. Geological Survey and Alaska Volcano Observatory announced around 2 p.m. (6 p.m. ET) Friday. This is down from the orange alert that had been put out Thursday.
"No new explosive activity has been observed since (Thursday) morning," reported the observatory, which is a joint venture between the USGS, Alaskan government and University of Alaska at Fairbanks.
The geological survey said that "continued activity (is) uncertain."
The Cleveland Volcano makes up the western half of uninhabited Chuginadak Island, part of the Aleutian island chain in the Bering Sea. It is about 45 miles west of Nikolski and 940 miles southwest of Anchorage.
The Thursday morning explosion produced a drifting ash cloud, as well as waves detected by a seismic network on Okmok Volcano, which is on the same Aleutian island as Nikolski.
Authorities also had an issued an orange alert in early September, amid concerns that the volcano could be leaking from its flanks if the lava inside continued to build up. The volcano's lava dome was 262 feet in diameter on August 30, but by then in had expanded to 394 feet. That warning was downgraded to yellow on November 3.
The Cleveland Volcano's last, most significant eruption came in February 2001, when three explosions created ash clouds that soared as high as 39,000 feet and spurred a hot avalanche that reached the water. Smaller ash emissions were detected in January, and before that in June 2009, the observatory said.
Even while lowering the alert level Friday, the volcano observatory cautioned that more activity could be coming.
Specifically, its online notice said that lava could go "over the crater rim and down the steep flanks of the volcano. Such lava flows might collapse and produce avalanches of hot debris that reach the sea and may be accompanied by small ash clouds."