Flight are resuming in Argentina and Chile after a huge volcanic ash brought air space across large part of South America to a standstill. However heavy rain around Puyehue volcano in Chile has prompted fears of mudslides.

Scores of flights were cancelled on Tuesday as the cloud drifted over Chile, Argentina, and into Brazil and Uruguay. Flights in and out of the Argentine capital Buenos Aires, a key regional hub, were cancelled for most of the day.

Uruguay’s main Carrasco airport was severely disrupted, with over 90 percent of flights cancelled. However officials have said the situation is expected to return to normal by Wednesday evening.

Flights to and from Buenos Aires, Mendoza and Cordoba are also restarting, according to LAN.

The Puyehue volcano is located about 540 miles south of Santiago in the Andes. Saturday’s eruption prompted Chilean authorities to order the relocation of at least 3,500 people as it sent a 10-kilometre-high ash cloud into the atmosphere.

Winds carried large quantities of ash across the Andes to Argentina. The popular tourist town of Bariloche, located about 850 miles to the southwest of Buenos Aires, was blanketed in ash.

Rain mixed with volcanic ash poured down on communities near the Puyehue volcano, raising fears that the weight of falling water and volcanic materials could cause mudslides and threaten dams in the area.

“We are concerned about water that can drag the volcanic material certain places and cause some dams to fall,” public works minister Hernan de Soliminhac said.

Enrique Valdivieso, director of Chile’s National Service of Geology and Mines said heavy rains could bring gases and ash to the surface, contaminating nearby rivers.

Valdivieso said that Puyehue’s eruptions have slowed but there is still a risk of large amounts of sediment pouring down from the eruption.