Mexico’s National Center for Prevention of Disasters reported volcanic tremors with emissions of gas, water vapor, and ash reaching heights of 2,000 meters from the active Popocatepetl volcano on September 11.

The center said 753 minutes of low-amplitude tremor were detected, as well as an explosion at 1:34 am.

The agency urged people not to approach the volcano “due to the danger posed by falling ballistic fragments” and possible mud slides in the event of heavy rain.