Evacuation of residents of residents living on the slopes of the Chaparrastique volcano in El Salvador has resumed.
The volcano started erupting on Sunday morning, emitting ash and gases.
Officials from the environment ministry said there was a risk the volcano could erupt again, this time emitting a lava flow.
The last time the Chaparrastique discharged lava was in 1976. It also caused a strong tremor in 2010.
During Sunday's eruption an ash cloud rose 5000 metres from the cone of the volcano. Since then, it has been emitting gases.
Volcanologist Francisco Barahona of the University of El Salvador said that a further increase in the emission of sulphur dioxide could be a sign that another eruption was approaching.
More than 2000 people were evacuated after the first eruption on Sunday, but the BBC rerports many have since returned.
Chaparrastique is one of more than 20 volcanoes in El Salvador. It is 140 km east of San Salvador.