A fourth man believed to be involved in a conspiracy to bomb New York subways last fall has been arrested in Pakistan and faces extradition to the United States, the New York Daily News reports.

The newspaper's account cites unidentified and undefined sources. It indicates the plan hatched by Najibullah Zazi was to simultaneously attack some of the city's most congested subway lines during rush hour last September. Zazi is cooperating with federal investigators after pleading guilty to conspiracy to use weapons of mass destruction and to providing material support to al Qaeda. According to the Daily News:

"Zazi and his two Queens friends allegedly planned to strap explosives to their bodies and split up, heading for the Grand Central and Times Square stations - the two busiest subway stations in New York City.

They would board trains on the 1, 2, 3 and 6 lines at rush hour and planned to position themselves in the middle of the packed trains to ensure the maximum carnage when they blew themselves up, sources said."

Adis Medunjanin and Zarein Ahmedzay have been charged with conspiracy to use weapons of mass destruction.

The plot traces back to a 2008 trip the men made to Pakistan to join the fight against American troops in Afghanistan. Al Qaeda operatives instead pulled the men aside for explosives training and reportedly sent them back to the U.S. Zazi was "given special bomb-making training because of his knowledge of the subway system."

The plot unraveled when U.S. intelligence learned of the plot from a Pakistani informant. Zazi was placed under surveillance and ditched his explosives after a traffic stop in New York. By then, the Daily News reports, he already had scouted subway routes repeatedly to determine "where to best spread death and mayhem."

Read the full Daily News report here.