Twin blasts from the Calbuco volcano in southern Chile sent vast clouds of ash into the sky, covering the town with thick soot and raising concerns that the dust could contaminate water, cause respiratory illnesses and ground more flights.

The volcano erupted on Wednesday afternoon for the first time in more than four decades, spewing out a plume of ash more than six miles high. Emergency officials were taken by surprise and had only a few minutes to issue an alert.

Most of the 1,500 residents had evacuated after the initial eruption on Wednesday, with only about 30 people refusing to leave out of worry for their homes and animals.

Calbuco volcano erupts near Puerto Varas. — AP

People clean an ash-covered roof of a house in Ensenada town. — Reuters

Children watch the Calbuco volcano erupt, from Puerto Varas, Chile.— AP

View of the Calbuco Volcano in La Ensenada, southern Chile, on April 26, 2015. — AP

A view of a square at Petrohue lake which was hit by ashes from Calbuco Volcano, in the vicinity of Puerto Montt city April 26, 2015. — Reuters

Swings covered by ash and lava from the Calbuco Volcano in La Ensenada, southern Chile, on April 26, 2015. — AFP

In this Wednesday, April 22, 2015 photo, the Calbuco volcano erupts near Puerto Varas, Chile.— AP

A local cleans a roof of a house next to Petrohue lake which was hit by ashes from Calbuco volcano, in the vicinity of Puerto Montt city. — Reuters

A car lies covered with ashes from Calbuco Volcano at the road to Petrohue lake, in the vicinity of Puerto Montt city April 26, 2015.— Reuters

Navy soldiers help to remove ashes from Calbuco Volcano at Ensenada town, in the vicinity of Puerto Montt city. — Reuters

Soldiers arrive to help near Ensenada town which is covered with ashes from Calbuco Volcano. — Reuters

A scarecrow is seen in a backyard of a house nearby Ensenada which is covered with ashes from Calbuco Volcano. — Reuters

Soldiers remove ashes from a house nearby Ensenada which is covered with ashes from Calbuco Volcano. — Reuters

Locals round up cows to be transported from Ensenada which is covered with ashes from Calbuco Volcano. — Reuters

Residents wearing surgical masks to protect themselves against ash from Calbuco volcano, walk in a street in Ensenada, Chile. — Reuters