The cellphone of Osama bin Laden’s trusted courier, which was recovered in the raid that killed both men in Pakistan last month, contained contacts to a militant group that is a longtime asset of Pakistan’s intelligence agency, senior American officials who have been briefed on the findings say.

The discovery indicates that Bin Laden used the group, Harakat-ul-Mujahedeen, as part of his support network inside the country, the officials and others said. But it also raised tantalizing questions about whether the group and others like it helped shelter and support Bin Laden on behalf of Pakistan’s spy agency, given that it had mentored Harakat and allowed it to operate in Pakistan for at least 20 years, the officials and analysts said.

In tracing the calls on the cellphone, American analysts have determined that Harakat commanders had called Pakistani intelligence officials, the senior American officials said. One said they had met. The officials added that the contacts were not necessarily about Bin Laden and his protection and that there was no “smoking gun” showing that Pakistan’s spy agency had protected Bin Laden.

But the cellphone numbers provide one of the most intriguing leads yet in the hunt for the answer to an urgent and vexing question for Washington: How was it that Bin Laden was able to live comfortably for years in Abbottabad, a town dominated by the Pakistani military and only a three-hour drive from Islamabad, the capital?

“It’s a serious lead,” said one American official, who has been briefed in broad terms on the cellphone analysis. “It’s an avenue we’re investigating.”

The revelation also provides a potentially critical piece of the puzzle about Bin Laden’s secret odyssey after he slipped away from American forces in the Tora Bora region of Afghanistan nearly 10 years ago. It may help answer how and why Bin Laden or his protectors chose Abbottabad, where he was killed in a raid by a Navy Seals team on May 2.

Relations with Pakistan could get rough — they had to know bin Laden was there (in Abbottabad) His million-dollar compound was less than 40 miles from Pakistan’s capital. That’s like escaping Washington, D.C. by hiding out in Baltimore. …And it turns out bin Laden was hiding out just 1,000 yards from the prestigious Kakul Military Academy, the ‘West Point of Pakistan.’ Now, in (the Pakistanis’) defense, the compound had very high walls, so they may have seen their neighbor only from the eyes up — like Wilson, from Home Improvement.