(CNN) -- Authorities in Guatemala say they've detected an increase in vibration inside a volcano that killed three people when it erupted in May.
Researchers recently detected "an increase in internal vibration" at the Pacaya volcano, about 18 miles (30 kilometers) south of Guatemala City. The increase could cause further eruptions, according to a statement from CONRED, an emergency agency of the Guatemalan government.
Seismologists have not ruled out a complete eruption that could, depending on the wind direction, bring ash and soot to the capital.
An eruption of the volcano in May killed three people and shut down the international airport in Guatemala City.