WASHINGTON - U.S. investigators have released a few more details about the terrorists who slammed passengers planes into the World Trade Center and Pentagon Tuesday.

There were a total of 18 hijackers on the jets, along with a large number of "associates" on the ground, according to U.S. Attorney General John Ashcroft.

The terrorists had all purchased tickets, he said Thursday. There were five hijackers on each of two planes, and four hijackers on each of the other two aircraft.

The FBI is pursuing "thousands and thousands of leads," Ashcroft told reporters, and he thanked the public for sending in tips.

The agency's 1-800 hotline has received more than 2,000 calls, and its Web site has logged close to 23,000 e-mails.

"Some of these leads have been helpful to the investigation,"Ashcroft said.

Authorities are hoping to find out more about the terrorists from the "black boxes" containing flight-data and cockpit conversations. The equipment, intended to remain intact after crashes, has not been found in either New York or Washington. But authorities said Thursday that they think they've detected a signal from at least one of the black boxes.

On Wednesday, officials said that at least one hijacker on each plane was trained at flight schools in the United States.

Prime Minister Jean Chrétien insisted Thursday that there is no evidence any of the hijackers entered the United States from Canada. Security remains tight at all border crossings and many government buildings.

Written by CBC News Online staff http://www.cbc.ca/cgi-bin/view?/news/2001/09/13/ashcroft_010913