A French publisher has apologised after a history textbook that appeared in bookshops in recent weeks suggested the 11 September 2001 attacks were probably "orchestrated by the CIA", reports BBC News.
The debunked conspiracy theory was apparently highlighted on social media initially by a group of schoolteachers.
The book History of the 20th Century in Flash Cards is aimed at undergraduate students.
On its website, the publisher said the phrase should never have appeared.
"This phrase which echoes conspiracy theories devoid of any factual basis should never have been used in this work. It doesn't reflect the editorial position either of Ellipses publications or the author," it said.
The textbook is described as a complete course on the last century in French, European and world history. It was written by Jean-Pierre Rocher, a teacher of history and geography and a graduate of the Sciences Po university in Paris, and aimed at Sciences Po undergraduates as well as students preparing for France's elite "grandes écoles".
Although the book came out in November, it was not until the daughter of one of the secondary school teachers bought a copy that one of them spotted the reference to the CIA.
On page 204 the author explains the context of the creation of the jihadist group, al-Qaeda and the "quadruple terrorist attack of 11/9 2001 on New York and Washington". He then makes the following statement.
"This global event - without doubt orchestrated by the CIA (secret services) to impose American influence on the Middle East? - hit the symbols of American power on its own territory."
The teacher immediately shared his concerns on a teachers' Facebook group whose spokesman, Bruno Modica, told Le Monde "it blew up very quickly".
"There were 122 comments; this inserted clause of his conveys a conspiracy theory you can hear in our classrooms, from some pupils' mouths; but to find it written by a teacher and in this type of publication is unacceptable."
The story was picked up by the Conspiracy Watch website, which complained that the sentence falsely suggested that there was some sort of controversy surrounding September 11th.
It pointed out that a survey carried out by Ifop in December 2018 had found that 21% of people under 35 backed the idea that the US government was implicated in the attacks, and that this was the age group targeted by the textbook.