If the dome stops growing and cools, that would raise the risks of an explosion

Jesus Muniz, volcanologist

Scientists have been warning that a major eruption is imminent at Colima for the past few days as a huge lava dome has formed in the volcano's crater causing a massive build up of pressure.

Colima, located about 500 kilometres (310 miles) west of Mexico City, is known as the Volcano of Fire and it is regarded as Mexico's most active volcano.

The dome of lava is 65 metres (213 feet) tall and covers practically the entire 185m diameter of the crater.

Earthquakes

For the last few days the pressure build-up has been causing rumblings and about 120 small earthquakes a day.

Volcanologists say an explosion of the expanding lava dome would cover the surrounding area with rock and ash, but if the dome collapses scientists are predicting that rivers of molten lava would flow down the southern slopes.

The volcano began to throw out rocks and lava on Tuesday, forcing the evacuation of 216 people from Yerbabuena, a village close to the peak.

Assisted by the army and Red Cross workers, residents were piled onto buses and taken to shelters in towns outside the 6.5km exclusion zone.

Soldiers helped the people load up their belongings and some remained behind to guard the village against looting, a spokesman from the Civil Protection Authority said.

Refusing to leave

But despite the threat of a major eruption, 12 villagers refused to leave, including 103-year-old Alberta Altamirano.

Fog has shrouded the slopes of the volcano, making it invisible from the ground, but scientists from the University of Colima have been using a reconnaissance plane to complete a survey of the volcano.

A exclusion zone has been set up around the crater

On Tuesday scientists from the university said one flight had revealed new lava flows and that the state of alert around the volcano would remain.

"If the dome stops growing and cools, that would raise the risks of an explosion," said Jesus Muniz, the co-ordinator for the volcano scientific committee.

The volcano last erupted in 1998 when lava reached villages five kilometres away, forcing 500 people to flee.

About 300,000 people live within 40km of the volcano, a radius that includes Colima city, the state capital, but in the past lava has never reached the populated areas.