Ash and smoke from erupting Mexican volcano Popocatepetl grounded flights earlier in the week, officials said.

Cars in the lot of the Puebla Airport were covered in ash. Flights were canceled on Tuesday but had resumed by Wednesday.

In the town of Xalizintla, near the volcano, veterinarians spent much of Wednesday implanting microchips in animals to help track them in case their owners are evacuated.

Last month, Mexico's National Centre for Disaster Protection raised the alert level for Popocatepetl, indicating possible magma expulsion and explosions of increasing intensity. It is the third-highest warning on the centre's seven-step scale.

The 5,483 metre (17,992 feet) volcano, whose name means "smoking mountain" in the Nahuatl Indian language, lies just 64 kilometres (40 miles) southeast of Mexico City and its 18 million residents.

"Popo," as the volcano is commonly known, has spat out mile-high clouds of ash and smoke several times this year.