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Mount St Helens volcano in the US state of Washington could erupt again very soon following a small eruption last week, scientists say.

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It was the first eruption since 1986 and spewed a plume of steam and ash into the sky.

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The volcano had been showing rumbles of activity for several days. Here, stream can be seen rising from the crater.

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Over the weekend, crowds of spectators gathered at viewpoints to marvel at the volcano, some wearing masks to keep out the dust.

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A dark section (left) shows where snow has melted from Friday's eruption.

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Spirit Lake, at the foot of the volcano, still contains debris from the more powerful eruption in 1980, which killed 57 people.

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The volcano's reawakening has prompted much interest from reporters.

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And residents in the states of Washington and Oregon are also hoping to witness an eruption, though from a safe distance.

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It may look calm, but the volcano is on highest eruption risk level, indicating there is a risk to life and property in the area.