Two federal biologists were rescued from a volcanic island just before it emitted a 35-thousand foot ash plume.

The biologists, who were studying birds, were rescued from volcanic Kasatochi Island in the Aleutians on Thursday.

Official said the escape allowed the unnamed biologists to escape burning flows of gas, steam and ash that reportedly enveloped the island.

"If they had been there, they certainly could have died," said Stephanie Prejean, U.S. Geological Survey seismologist with the Alaska Volcano Observatory.

Kasatochi is the third Aleutian volcano currently rumbling. Okmok began erupting July 12. Mount Cleveland erupted July 21.

Someone from Adak was able to rescue the pair in a boat, but that person wasn't immediately known.

The biologists were have been removed from the island Wednesday, but a helicopter that was to have rescued them had mechanical problems.

A Fish & Wildlife boat was too far away, and there was no immediate response from a call to fisherman for help, said Poppy Benson of the Alaska Maritime National Wildlife Refuge in Homer.

Early Thursday afternoon, someone from Adak was able to reach them by boat.

As they awaited arrival of the boat, Prejean said the shaking on the island grew increasingly intense, lasting about 20 minutes. She said they then began to smell sulfur gas, a sign of an impending eruption.

The ash plume caused an air travel advisory and was expected to drop ash on the neighboring community of Adak, Prejean said. Scientists have not been monitoring the volcano, and there's no record of when it last erupted, she said.