MOUNT ST. HELENS, Wash. -- Steam and ash have been intermittently spewing from a growing new lava dome inside the crater of Mount St. Helens, scientists with the U.S. Geological Survey said.

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IMAGES FROM THE MOUNTAIN Slideshow: Glowing Lava Oozes From Crater Slideshow: Large Plume Drifting North-Northeast Slideshow: Steam Eruption On 10-4 Slideshow: User Submitted Mount St. Helens Images Slideshow: Steam Vent Forms After Eruption Images: Mount St. Helens Gets Steamed Slideshow: Steam Shoots From Crater Webcam: Mount St. Helens VolcanoCam

The new lava dome has grown a protrusion the size of a 30-story building and it glows red at night.

The lobe began building up last month. One section has risen 330 feet in the past ten days.

Scientists said it is the result of rising magma, or molten lava.

Officials warned an eruption could occur suddenly or with very little warning. It could include volcanic debris flows that could descend on the Toutle River valley.

MOUNT ST. HELENS Video: Time-Lapse Of Dome’s Growth Video: Time-Lapse Of Fin Growth Video: Thermal Imaging Of Rock Avalanche Slideshow: Hulking Rock Slab Grows In Volcano's Crater Slideshow: Images From 3-8-05 Ash Plume Slideshow: Infrared Shots Of Activity At Mount St. Helens Slideshow: Dome In Mount St. Helens Crumbling Slideshow: Glowing Lava Oozes From Crater Slideshow: Large Plume Drifting North-Northeast Slideshow: Steam Eruption On 10-4 Slideshow: User Submitted Mount St. Helens Images Slideshow: Steam Vent Forms After Eruption Images: Mount St. Helens Gets Steamed Slideshow: Steam Shoots From Crater Webcam: Mount St. Helens VolcanoCam Complete Coverage Of Mount St. Helens

Scientists said lava spilling out of the crater is unlikely, but an explosive eruption could send significant ash thousands of feet above the crater and to areas downwind of the mountain.