"I started to look through all the drawings and each one had his fingerprint", she said, calling it an "OMG moment" at Tuesday's press conference in Paris.
Their opinion, "based on years of research on Van Gogh's drawings in the museum's own collection and elsewhere", was that the album drawings were imitations.
The Van Gogh museum in Amsterdam has dismissed an art historian's claim that a collection of discovered sketches were drawn by the Dutch artist, saying they were imitations.
Le Seuil had described the sketches as "a very impressive ensemble" and insisted that "their authenticity is well established".
The book claims the ink drawings were created in the accounts book of a hotel Van Gogh was staying at in the French city of Arles in 1888.
"And I looked at it and I saw all the things that Van Gogh stands for in terms of reed-pen brushwork, graphite underground work, the whole possible elements", she said, adding she had the drawings verified by various specialists.
According to the University of Toronto website, Welsh-Ovcharov has taught art history for 25 years and has created several Van Gogh exhibitions, including one at the Musee d'Orsay in Paris.
Two Van Gogh masterpieces stolen in Amsterdam 14 years ago have been recovered from the home of a notorious Italian drug boss near Naples, Italian and museum officials announced on September 30, 2016.
Researchers from the Van Gogh museum - widely accepted as the world's authorities on the artist - concluded that the style of the drawings were uncharacteristic of his work during the period and were unrefined, "clumsy" and "monotonous".
"The Van Gogh museum had seen a high definition set of drawings as photographs", Welsh-Ovcharov told reporters.
Sixty-five previously unknown drawings by the painter Vincent Van Gogh have been discovered, the French publishers Le Seuil said on Tuesday.
Some of the sketches include portraits of his friends Paul Gauguin and Pierre and Marie Ginoux, who owned the Café de la Gare where had stayed.
A LOST sketchbook belonging to artist Vincent Van Gogh has been found.
The team said another telling point was that the drawings in the sketchbook were executed in brownish ink, and this type of ink has never been found in Van Gogh's drawings from the period in question.