BALTIMORE/WASHINGTON – The director of the U.S. National Security Agency on Thursday offered a more detailed breakdown of 54 schemes by militants that he said were disrupted by phone and internet surveillance, even as a British newspaper offered evidence of more extensive spying.

In a speech in Baltimore, NSA chief General Keith Alexander said the list of cases turned over recently to Congress included 42 that involved disrupted plots and 12 in which surveillance targets provided material support to terrorism.

Alexander's assertions about the effectiveness of NSA surveillance came as Britain's Guardian newspaper reported that the NSA for years collected masses of raw data on the email and Internet traffic of U.S. citizens and residents.

Citing a top-secret draft report prepared in 2009 by NSA's inspector general, the Guardian said that the collection of what it described as "bulk internet metadata" began shortly after the attacks of Sept. 11, 2001.

Initially the program collected only information in which one party was outside the United States or communications between known foreigners. But the program expanded in 2007.

The paper said the Internet "metadata" comprised the addresses to and from which messages were sent, including IP addresses which could show a person's physical location. It quoted officials saying this particular collection effort ended in 2011.

In his speech to a communications and electronics industry group, Alexander said the NSA case list was provided late last week to several congressional committees. He said that 50 of the 54 cases cited had resulted in arrests or detentions.

He also said that 25 of the arrests or detentions occurred in Europe, 11 in Asia, and 5 in Africa. Thirteen of the plots occurred inside the United States, he added.

The latest Guardian revelations appear to show that NSA collected the same kind of raw Internet traffic data among people inside the United States as it collects on telephone users.

The Guardian also previously published secret documents about an NSA program called Prism, which gave NSA the capability to search the content of traffic sent through U.S. Internet companies by foreign intelligence subjects. The paper's latest revelations do not discuss the searching or examination of email content.

In his speech, Alexander said that 12 foiled plots involved using material gathered under the agency's raw telephone data collection program.

He said that in 53 of the 54 cases, the agency also had used its authority to eavesdrop on internet traffic of foreign intelligence targets. The actions allowed the U.S. to collect data which "played a critical role."

Alexander said that almost half of NSA's counter-terrorism reporting came from internet monitoring.

The Guardian report said that NSA collection of internet metadata initially began under a controversial warrantless wiretapping program authorized by the administration of President George W. Bush, but was later authorized by the secretive Foreign Intelligence Surveillance Court.

The Guardian quoted Shawn Turner, chief spokesman for the U.S. Director of National Intelligence, saying that the collection program, which continued after Barack Obama became president, was terminated in 2011 "for operational and resource reasons and has not been re-started."

Now shut down

In his comments, which apparently responded to the latest Guardian story, Alexander acknowledged that NSA's email metadata collection program had been "analogous" to its telephone call data collection. He said the program had ceased because "it didn't have the operation impact that we needed."

"Because it wasn't meeting what we needed and we thought we could better protect civil liberties and privacy by doing away with it, Alexander said. He added: "And all that data was purged at that time."

However, the Guardian said that it had seen other secret NSA papers suggesting that some online data collection continued today.

Previously, citing documents provided by former NSA contractor Edward Snowden, the Guardian published a secret court order authorizing NSA to collect masses of similar "metadata" charting traffic between phone numbers. The order, covering calls both within the United States and between the United States and foreign countries, had been re-issued as recently as April 2013.

The Guardian's latest story said that when NSA began collecting Internet metadata in 2001, the agency was limited to only cases where "at least one communicant" was located outside the United States "or for which no communicant was known to be a citizen of the United States."

However, the Guardian printed what it said was a 2007 secret U.S. Justice Department memo. It said the memo indicated that NSA later got authority to "analyze communications metadata associated with United States persons and persons believed to be in the United States."

A top secret draft report on the email program prepared by NSA's inspector general, and posted on the Guardian's website, makes clear the key role played by private companies, who partner with NSA. In the report's words, they help the U.S. government "obtain access to information that would not otherwise be available."

The report describes how, in early October 2001, NSA officials approached three major U.S.-based communication service providers - identified in the report as COMPANY A, COMPANY B, and COMPANY C - to seek cooperation with the new surveillance program. "Each company agreed to cooperate," the report says.

The report adds that between Oct. 16, 2001 and Dec. 14, 2006, NSA sent 147 letters requesting assistance to five unidentified companies.