LONDON – Laying out preliminary evidence in what they called an “immense” conspiracy, British prosecutors announced terrorism-related charges Monday against 11 of the 23 people in connection with an alleged plot to blow up trans-Atlantic flights to the United States.

Eight of the 11 were charged with conspiracy to commit murder and preparing to commit acts of terrorism. Among those named was Abdullah Ali Ahmed Khan, 25, also known as Ahmed Abdullah Ali, who was named by a U.S. intelligence source as the chief “facilitator” of the plot.

Two others have been charged with failing to disclose information, and a 17-year-old male – the youngest suspect – has been charged under Britain’s new anti-terrorism laws with being in possession of a book on bomb-making and the suicide notes and wills of those who were prepared to blow themselves up.

One female suspect was released without being charged.

Peter Clarke, head of Scotland Yard’s anti-terrorism branch, confirmed that investigators have recovered bomb-making equipment and manuals, chemical components and several “martyrdom” videos, which terrorists have been known to record before suicide attacks.

Clarke said that evidence had been obtained in 69 searches from more than 400 computers, 200 cell phones and 8,000 items of removable storage media such as memory sticks, CDs and DVDs. He said a large amount of evidence also had been compiled from wiretaps and video surveillance of the suspects prior to their Aug. 9-10 arrests.

“The investigation is far from complete. The scale is immense. Inquiries will span the globe,” Clarke said in a press conference that lasted eight minutes. “The enormity of the alleged plot will be matched only by our determination to follow every lead and every line of inquiry.”

Nine of the 11 charged Monday, including a woman, live in London, most of them in and around Walthamstow, an ethnically diverse working-class community in east London. Two are from High Wycombe, about 25 miles from London.

Several of the alleged plotters prayed at the Umer mosque in Walthamstow, and their arrests nearly two weeks ago stunned neighbors who almost uniformly described the suspects as polite young men whose only notable characteristic was their conspicuous devotion to their religion.

Neighbors were confounded by the arrest of Waheed Zaman, a 22-year-old biomedical student at London Metropolitan University, where he was head of the student Islamic Society.

In addition to Khan and Zaman, the others charged with conspiracy to commit murder were identified as Adam Khatib, Tanvir Hussein, Arafat Waheed Khan, Assad Ali Sarwar, Ibrahim Savant and Umar Islam. Savant and Islam have been described as recent converts to Islam.

The eight charged with conspiracy are accused of planning “to smuggle the component parts of improvised explosive devices onto aircraft and assemble and detonate them on board.”

Authorities believe the terror cell was planning to explode the bombs on up to 10 fights bound for the United States. But thus far, they have revealed few details about the inner workings of a plot that may have had its origins in Pakistan.

Clarke, who took no questions at the press conference, would say only that the investigation would take many months to complete.

“There will be thousands of forensic examinations and comparisons. Fingerprints, DNA, electronic data, handwriting comparisons, chemical analysis and, indeed, the full range of forensic disciplines will be used,” he said.

The 11 detainees who have not been charged are still under active investigation, according to authorities. Among them is Tayib Rauf, the brother of Rashid Rauf, a Briton who was arrested in Pakistan and has been identified by intelligence officials as a liaison between the London conspirators and the plot’s masterminds.

Tayib Rauf was on a list of initial suspects whose bank accounts were frozen by the Bank of England last week.

The deadline for seeking a further extension of the uncharged suspects’ detention is Wednesday.