Oslo, Norway ? When police arrested a suspected al-Qaida cell in Norway last month, they turned up the makings of a bomb lab tucked away in a nondescript Oslo apartment building.

An Associated Press investigation shows that authorities learned early on about the alleged cell by intercepting e-mails from an al-Qaida operative in Pakistan and — thanks to those early warnings — were able to secretly replace a key bomb-making ingredient with a harmless liquid when one of the suspects ordered it at an Oslo pharmacy.

Officials say the suspected plot against this quiet Nordic country was one of three planned attacks on the West hatched in the rugged mountains of northwest Pakistan by some of al-Qaida’s most senior leaders. The other plots targeted the bustling New York subway and a shopping mall in Manchester, England.

Interviews with U.S. and European intelligence officials and documents reviewed by the AP paint the picture of a loosely organized cell that was doomed to fail long before Norwegian police raided its basement lab in suburban Oslo in July. The officials spoke on the condition of anonymity because they were not authorized to discuss the cases publicly.

The Norwegian plot’s undoing, and that of its sibling plots in the U.S. and Britain, casts light on the potential pitfalls of al-Qaida’s changing tactics in the decade since the massive, highly organized Sept. 11 attacks. In recent years, al-Qaida has grown increasingly decentralized and nimble, relying on amateurs to recruit local cells and carry out smaller-level attacks without extensive planning and hands-on training.

While such plots are harder to detect, they are also harder to manage — and the slack remote control they often require leaves greater room for operational error and sloppy tradecraft.

All three plots were thwarted after suspected operatives exchanged e-mails — sometimes poorly coded ones — in and out of Pakistan.

Authorities say the ringleader of the Norwegian plot is 39-year-old Mikael Davud, a Uighur who came to Norway in 1999 as part of a U.N. refugee program and then became a Norwegian citizen eight years later. Uighurs, a largely Muslim ethnic group in China, claim oppression at the hands of authorities there.

Davud was arrested July 8 along with suspected accomplices Shawan Sadek Saeed Bujak Bujak, a 37-year-old Iraqi Kurd, and a 31-year-old Uzbek national, David Jakobsen. Both are permanent residents of Norway.

The trio deny any connection to terrorist groups.

Davud’s path to the al-Qaida plot began in Turkey, where he and his wife traveled in the fall of 2008, according to documents and officials.

There, Davud met an al-Qaida facilitator who remains at large but has been identified by investigators. That winter, he traveled from Turkey to a al-Qaida training camp in Waziristan, a lawless tribal region in northwestern Pakistan.

In May 2009, shortly before he returned to Norway, Davud sent an e-mail to a Gmail address that authorities believe belonged to a midlevel al-Qaida operative in Peshawar, Pakistan, known as Ahmad. Ahmad also communicated with the New York and Manchester plotters, via a Yahoo! Mail account accessed at the same computer, and he is one of the key links connecting the plots, officials said.

This long-distance coordination — and the electronic trail it leaves behind — helped intelligence officials unravel the plans.