ANCHORAGE, Alaska (AP) — Another volcano in Alaska is heating up, with seismic instruments signaling a possible eruption, scientists said Monday.

Tremors were detected at Pavlof Volcano, 625 miles southwest of Anchorage, according to the Alaska Volcano Observatory. Satellite imagery showed the mountain was "very, very hot," said John Power, the U.S. Geological Survey scientist in charge at the observatory.

The aviation alert level for Pavlof was raised from "yellow" to "orange." A major ash emission could threaten international flights.

Pavlof is 37 miles from the community of Cold Bay, which was notified of the new activity that began about 8 a.m. Monday. Because of clouds, the volcano was not visible to the village of 100.

The volcano last erupted in 2007, but residents there said that eruption had no impact on Cold Bay, likely because the winds blew any ash fall away. Ash clouds were visible to residents, however.

"It was prominent," said Mike Tickle, manager of the local fuel terminal. "You could see it from all over the place."

Pavlof is the second Alaska volcano to rumble this month.

Cleveland Volcano, on an uninhabited island in the Aleutian Islands, experienced a low-level eruption in early May. Satellite imagery shows the volcano continues to discharge steam, gas and heat, although no ash clouds have been detected in the past week, Power said.

Cleveland is not monitored with seismic instruments. Its alert level remains at orange.

Pavlof's 2007 eruption lasted 29 days. It emitted mud flows and erupting lava, as well as ash clouds up to 18,000 feet high, Power said. At night, the 8,262-foot volcano glowed.

Typically, Pavlof eruptions are gas-rich fountains of lava that can shoot up to a few thousand feet. But its ash clouds are usually less dense than plumes of more explosive volcanoes that pose a greater hazard to aircraft, said volcanologist Game McGimsey.

No ash clouds were immediately detected Monday, and local air traffic controller Craig Jackson said there were no flight interruptions.

Pavlof is among the most active volcanoes in the Aleutian arc, with nearly 40 known eruptions, according to the observatory.

Cleveland is a 5,675-foot peak on a remote island 940 miles southwest of Anchorage. The volcano's most recent significant eruption began in February 2001 and sent ash clouds as high 39,000 feet above sea level. It also produced a rubbly lava flow and hot debris that reached the sea.

The most recent minor ash emissions from Cleveland were observed last November.