London ? Police found martyrdom videos and bomb-making components during the investigation of the alleged plot to blow up U.S.-bound jetliners, prosecutors said Monday in announcing 11 people had been charged with terrorism offenses.

Officials confirmed for the first time that the plot involved the manufacture of explosives, which were to be used to assemble and detonate bombs inside as many as 10 airliners. U.S. officials previously had said the plot appeared to involve mixing liquid-based chemicals to make explosives aboard the aircrafts.

One woman was released from custody Monday and police continued to interrogate 11 others who remain “under active investigation,” lead prosecutor Susan Hemming said.

Those charged were scheduled to appear in court this morning, but because of the seriousness of the accusations, it was unlikely bail would be granted.

The briefing by police and prosecutors lasted less than eight minutes, but provided more information than had been released in the 11 days since the alleged plot was first disclosed and air travel out of Britain was thrown into turmoil.

They said investigators had found bomb-making materials – including hydrogen peroxide and electrical components – and seized more than 400 computers and 200 cell phones in nearly 70 searches.

More than 8,000 items used for data storage, such as compact discs, DVDs and memory sticks, were reported found. Maps of Afghanistan, suicide notes from willing terrorists and books on explosives also were seized, officials said.

“We have also found a number of video recordings – these are sometimes referred to as martyrdom videos,” said Assistant Deputy Commissioner Peter Clarke, who leads the Metropolitan Police’s anti-terrorism unit. “This has all given us a clearer picture of the alleged plot.”

According to dates given by prosecutors, the plot could have begun last year.

The details of the charges against one man, Mehran Hussein, allege he had information that could have prevented a terrorist act and didn’t disclose it sometime between Sept. 23, 2005, and Aug. 10, 2006 – the day police announced breaking up the plot.

In all, eight people were charged with conspiracy to commit murder and preparing acts of terrorism. One person, a 17-year-old, was charged with possession of articles that could be used to prepare a terrorist act and two people were charged with failing to disclose information that could help prevent a terrorist act.

Nine of those charged were from London, according to a Bank of England list of suspects whose assets were frozen following the arrests.

Two were from High Wycombe, 30 miles northwest of London.

The briefing was also a chance for police to show they were avoiding missteps in previous terror investigations that had aroused considerable public skepticism over their actions. Clarke did not mention two earlier events but pledged that investigators would be diligent.