Investigators on three continents worked to fill in the full, frightening picture Friday of a plot to blow U.S. jetliners out of the Atlantic skies, tracking the money trail and seizing more alleged conspirators in the teeming towns of eastern Pakistan.
One arrested there, a Briton named Rashid Rauf, is believed to have been the operational planner and to have connections with al-Qaida in Afghanistan, Pakistani and U.S. officials said.
British and Pakistani authorities have arrested as many as 41 people in the two countries in connection with the alleged suicidal plan, broken up by British police this week, to detonate disguised liquid explosives aboard as many as 10 planes bound from Britain to the United States.
"The terrorists intended a second Sept. 11," said Frances Fragos Townsend, White House homeland security adviser.
New information underlined how close they were to mounting attacks.
After the first arrests in Pakistan some days ago, word went from Pakistan to the London plotters to move ahead quickly, a message intercepted by an intelligence agency, a U.S. official disclosed on condition of anonymity. That prompted British police to move in on the conspirators, long under watch.
British Home Secretary John Reid told reporters officials were confident the main suspects in the plot were in custody. But authorities "would go where any further evidence takes us," he said.
"I think it's pretty clear that in this case, we don't have everybody," Townsend told The Associated Press in Washington.
The British government released the names of 19 of the 24 arrested in Britain - many apparently British Muslims of Pakistani ancestry - and froze their assets. One of the 24 detainees later was freed.
The record of financial transactions, along with telephone and computer records, may help investigators trace more people in the alleged plot.
"Think of it as a river - you look upstream to find the source, and downstream to find out where the money is going," said Cliff Knuckey, former chief money laundering investigator for Scotland Yard.
American authorities were looking for any U.S. links in the conspiracy. Hundreds of FBI agents checked possible leads the past few weeks, including what two U.S. counterterrorism officials said, on condition of anonymity, were calls the British suspects placed to several U.S. cities.
But the U.S. homeland security secretary said Friday nothing significant had emerged. "Currently, we do not have evidence that there was, as part of this plot, any plan to initiate activity inside the United States or that the plotting was done in the United States," Michael Chertoff said.
Britain kept its threat assessment level at "critical," indicative of an imminent attack. Extraordinary security measures continued at British airports, although the backlog of passengers eased from Thursday's chaotic conditions, when hundreds of flights were canceled.
At Heathrow, Europe's busiest airport, around 70 percent of flights operated Friday, but many people turned around and headed home after an announcement that a raft of flights had been canceled, including British Airways services to San Francisco and Los Angeles.
At U.S. airports, airlines were recruiting more baggage handlers as U.S. travelers - facing new rules banning almost all liquids from carry-on luggage - adapted by checking bags they normally would have carried aboard. American passengers faced a second level of security checks starting Friday, with random bag searches at boarding gates.