Four U.S. airlines canceled flights to and from Mexico City on Friday, a day after ashes fell from Mexico's volcano Popocatepetl, a spokesman for Mexico City's international airport informed.

Alaska Airlines, United Airlines, Delta and AirTran canceled at least 10 flights to and from Mexico City on Friday, the spokesman told the news agency AFP. Airplanes' engines can be damaged by ashes.

Mexico City's National Airport is keeping passengers updated with the latest cancelations via it's Twitter page at @AICM3.

The risk level remained unchanged at "yellow Phase 2" on Friday, the second highest out of four levels. The alert indicates that while there is more activity, there is no risk of eruption.

On Thursday, as much as 60 flights were canceled after the volcano who had been on yellow alert since June 7, threw ashes. The streets in towns near the volcano and as far as Mexico City were covered in ashes and authorities have issued alerts to people to take cover and avoid inhaling them.

According to a report Friday from the National Center of Disaster Prevention, the volcano registered low quakes accompanied by a column of gas and ashes.