(CNN) -- Rumblings from Mexico's most well known volcano forced several U.S. airlines to cancel flights in the country's capital on Thursday.
Popocatepetl volcano has let out nearly 100 bursts of steam, gas and ash in the past 24 hours, the National Center of Disaster Prevention said.
The ashes haven't reached Mexico City International Airport, airport officials said in Twitter posts. But Delta, American Airlines and Alaska Airlines canceled a dozen flights that had been scheduled to depart from the airport on Thursday.
At the nearby Toluca International Airport outside Mexico City, Spirit Airlines canceled flights to and from Ft. Lauderdale and Dallas.
No Mexican airlines had canceled flights at the airports, officials said.
After detecting elevated activity, authorities flew over the volcano on Thursday. Disaster officials said they had measured 12 hours of tremors of high and medium frequency at the volcano, which is about 50 miles away from Mexico City's airport.
Located in a national park southeast of the capital, Popocatepetl can be seen from there on a clear day. It is one of Mexico's highest peaks and last had a major eruption in 2000.
But there have been rumblings since then. In April, authorities barred people from getting close to the volcano after a series of explosion and expulsions of ash and gas.