Lascar volcano, which sits in the Andes, rumbled into action on Saturday, triggering minor earth tremors.
BBC reports no damage in the surrounding area has so far been reported, but an initial green warning was raised to yellow.
Chile's National Geology and Mining Service (Sernageomin) defines "yellow" as meaning a volcano is unstable.
The classification also means experts are monitoring a site for minor explosions and appearances of smoke, according to Sernageomin.
