Meanwhile, Spanish investigators and intelligence officials are struggling to determine who exactly "Muhammad the Egyptian" is and how big a role he played in the bombings.

But in picking through the hundreds of detainees at Guantánamo Bay, military investigators have struggled to find more than a dozen they can tie directly to significant terrorist acts, officials said.

In Washington state, investigators were still struggling to analyze the Pacific Northwest murder spree that had ended as abruptly as it had begun.

As two dozen more cases quickly showed up here, investigators struggled to figure out whether the virus was spreading through personal contact, food or water.

In federal, state and local agencies where investigators have struggled to curb abuses in the boom-and-bust psychic hot line industry, tracking a phone line to its source is a familiar problem.

In the past, investigators had struggled to find a hard link to the 19 hijackers or their associates.

According to The Sunday Times, "American and German investigators have struggled to find evidence of Atta's whereabouts in January 2000 after he disappeared from Hamburg.

American and Egyptian investigators are struggling to determine whether the words exchanged between the captain when he returned and Mr. Batouti represent an argument or an effort to save the plane.

Hundreds of people called in claiming to be the sniper, and later on, investigators struggled to determine which calls had actually been placed by the sniper.

Even as American and Egyptian investigators struggled to sort out the cause, lawyers in the United States who specialize in aviation disasters said that they were planning lawsuits against EgyptAir.