The history textbook, History of the 20th Century in Flash Cards by Jean-Pierre Rocher, was intended for undergraduate students.
During a chapter explaining conflicts in the Middle East, the book describes the creation of al-Qaeda and the ”quadruple terrorist attack of 11/9 2001 on New York and Washington”.
On page 204, the author adds: ”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 book’s publisher, Ellipses, said the phrase should not have appeared in the book and the author wanted to delete the sentence.
“This phrase, which echoes conspiracy theories devoid of any factual basis, should never have been used in this book,” the publisher said in a statement.
“It does not reflect the editorial line of Ellipses or the position of its author.”
The publisher said it would also add a correction slip to the books which had not yet been sent to bookshops, the BBC reported.
The conspiracy theory was noticed by a secondary school teacher whose daughter bought a copy of the textbook.
Mr Modica said: “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 website Conspiracy Watch criticised the segment, which it said “misleadingly suggests” there was a historical controversy about the terror attacks.
It cited an Ifop poll carried out in December 2018 which found 21 per cent of those under 35 agreed with the idea that the US government was involved in the attacks, saying this was the age group the book was intended for.
The site said the author had said he “does not support conspiracy theories at all” and recognised the ambiguity of the sentence was “confusing” and “escaped” him during proof reading.
It comes as Khalid Sheikh Mohammed, the man accused of being the mastermind behind the attacks on the World Trade Centre and the Pentagon (one of the hijacked planes crashed in a field in Pennsylvania).
Some 2,997 people were killed in the attacks.