An Algerian charged by U.S. authorities with assisting in a terrorist bombing plot has begun to cooperate with American investigators and has provided details about the small network that allegedly planned the attack, according to an FBI affidavit made public here today.

The informant, Abdel Ghani Meskini, spent several days in Seattle with another Algerian, Ahmed Ressam, before Ressam was arrested Dec. 14 while carrying 200 pounds of explosive materials, the affidavit said.

Meskini's cooperation came to light today during a hearing in which a Montreal judge denied bail to Mokhtar Haouari, another alleged Algerian conspirator, who has been indicted on charges of aiding and directed Ressam's activities on the West Coast.

Meskini, who had been living in Brooklyn, N.Y., was arrested on Christmas day after police found his telephone number in Ressam's pocket. The FBI also revealed that it has at least one other informant with close ties to the group.

According to testimony and affidavits submitted today, the network was an outgrowth of a radical Algerian organization called the Armed Islamic Group, or GIA, which now has cells in Montreal, New York and Boston.

The network made extensive use of false documents and identities to cover up its activities and was financed largely through credit card and bank card fraud, according to the court documents. Police believe Ressam and other members attended a training camp for Islamic militants in Afghanistan.

Quebec Superior Court Judge Jean-Guy Boilard, who denied Haouari's request for bail, ruled that the information presented by investigators about an international terrorist conspiracy was "serious and credible." Boilard noted that Canada had become a natural haven for Algerian extremists because of its liberal immigration laws and the government's decision in 1996 not to deport Algerians out of fear that their government might torture or kill them.

The judge noted that Haouari, 31, has been in Canada since arriving in 1994 on a false passport and saying that he was fleeing extremists in the Islamic Front, another Algerian radical group, for which he once was an organizer. Since then, he has been arrested on charges of credit card fraud and has collected welfare while avoiding deportation by circumventing the Canadian immigration and legal system.

In Seattle, a federal grand jury indicted a seventh individual in the connection with the alleged conspiracy, Abdelmajid Dahoumane, an Algerian friend of Ressam's who is still at large. Dahoumane's indictment was contained in a superseding indictment filed against Ressam. In the new indictment, both men are charged with one count of crossing the border in a conspiracy to "destroy or damage structures," which carries a maximum of 25 years imprisonment. The indictment says their activities began sometime in 1998.

The two were also charged with reckless disregard for the safety of human life by "placing" explosives on the Port Angeles ferry, where Ressam was arrested on Dec. 14. That federal violation carries a maximum prison term of 20 years. The indictment suggests, but does not state, that Dahoumane might have been the individual whom law enforcement officials believe accompanied Ressam on the ferry and who has been described as having eluded notice and capture.

Much of what investigators now know about the GIA network in North America comes from Meskini, who was arrested in New York on Dec. 30 after FBI agents saw him trying to discard a plane ticket and other documents that would have shown he had been with Ressam in Seattle in the days prior to Ressam's arrest. Meskini pleaded not guilty today in a New York court to charges that he was part of the bomb smuggling operation.

According to investigators, Haouari dispatched Meskini to Seattle to drive and interpret for Ressam on Dec. 11 and used a bogus bank card to provide Ressam with fresh funds. When Ressam was arrested on Dec. 14, Meskini was apparently waiting for him to drive off the ferry, where he was supposed to leave the explosive-laden van in the parking lot for another, unknown network member to drive to its ultimate destination. The plan was foiled when U.S. Customs agents stopped Ressam and arrested him as he tried to run away.

While the information released today begins to remove some of the mystery surrounding the alleged activities of the GIA, it did not give any hint of what Ressam and his associates intended to do with the explosives in his car or even why the United States had been targeted. The GIA is the most violent of several militant Islamic groups opposed to Algeria's military-backed government.

U.S. counterterrorism officials say there is no evidence that the GIA's leadership has decided to open a new front in the United States. In the past, much of GIA's activities have been aimed at France, Algeria's former colonial ruler.

Based on the evidence gathered thus far, the officials say, the most important point is that several of the suspects appear to have received military training at camps in Afghanistan.

Informants also have told investigators that members of the Canadian cells were interested in fighting on behalf of Muslims under attack in Bosnia and Chechnya.

Today's hearing revealed the painstaking process by which investigators have pieced together a picture of the GIA's activities.

When Ressam was arrested, police found a piece of paper in his pocket bearing Meskini's Brooklyn telephone number and placed him under surveillance shortly after he returned from Seattle on Dec. 17.

Two days later, he read of Ressam's arrest and called Haouari in Montreal, who told him to get rid of his pager and cellular phone, destroy any evidence of his Seattle trip and move to a new apartment. As Haouari feared, the call gave police a solid link to Montreal. Subsequent checks of phone records revealed other contacts between the two dating to November.

Four days later, a surveillance team watched as Meskini left his Brooklyn home and walked to a nearby supermarket where he discarded several documents in a dumpster. A subsequent search of the dumpster found a receipt for Meskini's airplane ticket from Seattle along with four withdrawal slips from a Seattle automated teller machine, all in the name of Eduardo Rocha.

When Meskini was arrested on Christmas, a false passport, Social Security card and bank card in Rocha's name also were found in his possession or in his apartment.

Staff writers Lorraine Adams and John Lancaster in Washington and researcher Philippe Germain in Montreal contributed to this report.