WASHINGTON, Oct 18: US officials questioned suspected “unlawful combatants” being held at the US naval base at Guantanamo Bay, Cuba, about the Washington-area sniper, who has killed nine people since early this month, but they do not believe there is a connection, an official said on Friday.

“We have to cover all the bases,” an official said, while pointing out that this is not a new direction in the investigation.

It is a “logical step” in the case, the official noted.

The United States is holding some 560 suspected Al Qaeda and Taliban fighters captured during US operations in Afghanistan at the naval base in Cuba.

Law enforcement officials in Manchester, England, had reportedly earlier seized a manual on assassinations using firearms believed to have been written by Al Qaeda.

Police shared “optimism,” not progress, on Friday in the search for the elusive sniper, as spy planes were readied to criss-cross Washington and outdoor events around the area were cancelled.

“I remain very optimistic,” Montgomery County police chief Charles Moose told reporters.

“I’m an optimistic person.”—AFP