MEXICO CITY - Mexican authorities raised the alert level for the Popocatepetl volcano near to Mexico City on Monday after it started spewing red-hot fragments of rock.

The lava dome of Popocatepetl, some 50 miles (80 km) to the southeast of the capital, started to expand on Friday, Mexico's National Center for Disaster Prevention said.

This change in activity in the 5,450 meter (17,900 foot) volcano could provoke big explosions capable of sending incandescent fragments out over considerable distances, as well as ash showers, the center said in a statement.

The center raised the alert level to yellow phase three from yellow phase two, indicating possible magma expulsion and explosions of increasing intensity. It is the third-highest warning on the center's seven-step scale.

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