Washington ? Osama bin Laden’s warning this week about an upcoming attack on the United States answered at least one question about the al-Qaida leader: He is still alive, or at least was until very recently.

But it opened a new inquiry by counterterror officials who are analyzing the bin Laden audiotape for clues about when and where it was made – and, most importantly, whether it sends a signal to carry out his threat.

Intelligence analysts were scrutinizing the recording for any clues – including certain words and phrases – that might be a signal for the terror network’s members or followers. They spoke on condition of anonymity because they were not authorized to speak publicly about the matter.

The Homeland Security Department said it had no plans to raise the nation’s terror threat-alert level and no reason to believe an attack was imminent.

“We, of course, have been very concerned about the threat of terrorism, generally, since the attacks of 9-11,” Atty. Gen. Alberto Gonzales said. “And obviously we expect the American people to live their lives as normally as possible.”

The audio recording was the first public statement by bin Laden since December 2004. That is the longest stretch the terror leader has been publicly quiet since the attacks of Sept. 11, 2001.

Authorities would not say whether the recording indicates anything about bin Laden’s whereabouts or health.

A counterterror official said analysts believe the tape appears to have been recorded since December, although it was not clear how recently – or if it was in response to U.S. missile strikes in Pakistan last week that Pakistani authorities said killed four senior al-Qaida operatives.

The Arab television network Al-Jazeera, which released the tape Thursday, initially reported it was made in December but corrected itself later to say it was recorded this month. Editors at the station said they could not comment on how they knew when it was made.