Air traffic has been advised to steer clear of the volcano
The Mount St Helens volcano has erupted in the US, sending a cloud of ash and smoke nearly 12,000m (40,000ft) into the air.
The eruption comes after weeks of heightened seismic activity, marked by tremors and mudslides.
It is not believed to pose any threat to people in the sparsely populated area of Washington State.
An eruption 25 years ago killed 57 people and coated nearby towns in a layer of ash.
A smaller eruption was reported in 1986 but did not cause severe damage. It is not known if any lava was released during the latest event.
Air traffic controllers have advised all flights to steer clear of the area.
An official from the state's emergency management service told AFP news agency the eruption happened at 1730 on Tuesday (0130 GMT Wednesday).
"We are monitoring the situation," he said.
The eruption followed a 2.0 magnitude quake on the eastern side of the mountain, a University of Washington seismologist told the Associated Press agency.
The scientist warned a larger eruption could happen at any time.
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Air traffic controllers have advised all flights to steer clear of the area.
