Yellow police tape blocked the entrance to the Taubman building at the John F. Kennedy School of Government for 30 minutes Tuesday, as U.S. Army ordinance technicians tried to determine the cause of a suspicious odor.

As the President of Tanzania addressed a Kennedy School crowd just yards away, Army hounds put their noses to the ground and U.S. Secret Service agents stood watch nervously.

It was all in vain.

"They sniffed out a cable box," said Sgt. William McNamara of the Harvard University Police Department (HUPD).

An engine and truck from the Cambridge Fire Department (CFD) initially responded and assisted with the search, said a police official on the scene.

"It's clear, it's clear," said the CFD's on-scene commander as he packed his protective gear in the back of his car.

Neither HUPD, the CFD, the Cambridge Police Department, nor the Secret Service would comment on who initially smelled the odor.

It was unclear whether the heightened search to discover the odor was triggered because a foreign dignitary was speaking nearby.

As a head of state, the President of Tanzania is accorded protection by the Secret Service when he travels in the U.S, although such protection is usually limited to a squad of a dozen agents.