A painting by Vincent Van Gogh has been found by the Van Gogh Museum in Amsterdam.  The painting was in a Norwegian attic for years and was long thought to have been painted by another artist, the Associated Press reports.

The picture, entitled "Sunset at Montmajour" is a landscape painting. Green trees growing between yellow grass and bushes are painted among blue and white skies. Van Gogh's trademark thick brush strokes are apparent in the work.  

At the unveiling ceremony of the piece, Axel Rueger, Van Gogh Museum director, said discovering the painting was a "once-in-a-lifetime experience."

"Sunset at Montmajour" is the first full-sized canvas painting by Van Gogh to be discovered since 1928. The work was painted July 4, 1888. Historians determined this because Van Gogh wrote about the painting in a letter to Theo, his brother, on that date.

According to Van Gogh's letter, the painting was created "on a stony heath where small twisted oaks grow." The location has been determined to be Arles, France, where Van Gogh lived at the time. The area lies near the ruins of an abbey, which are seen in the left side of the painting's background, and Montmajour hill.

Experts at the Van Gogh Museum determined the artwork's authenticity by its style, letters and the tangible materials used to create it. The experts also traced the painting's history.

The museum did not reveal much about the painting's discovery. They did, however, say that the work belonged to a Norwegian man who was told that the piece was not a Van Gogh. Consequently, he put the work in his attic.

Rueger told the Associated Press that the museum did not think the painting was authentic in the 1990s, partially because it lacked the artist's signature. A two-year-long investigation with new techniques changed the museum's mind.

According to Teio Meedendorp, a researcher, investigators of the piece "have found answers to all the key questions, which is remarkable for a painting that has been lost for more than 100 years."

"Sunset at Montmajour" has the number 180 written on the back, marking it as number 180 in Theo van Gogh's collection. The piece was sold in 1901. Currently, the painting belongs to a private collector. The piece is large, measuring 36.7 by 28.9 inches.

Meedendorp said that the newly-discovered painting is part of "a special group of experimental works that Van Gogh at times esteemed of lesser value than we tend to nowadays."

"Sunset at Montmajour" will be on display at the Van Gogh Museum starting Sept. 24.  The museum owns 140 examples of the Dutch artist's work.