Money Trail Eludes Officials in Probe of N.Y. Bombing : Blast: Investigators had hoped to trace funds to a known terrorist group, or to Iran or Iraq. Evidence so far can’t rule out a home-grown plot.

Three weeks after determining that money from overseas flowed to some suspects in the World Trade Center bombing, federal investigators have been frustrated at their inability to find the source of the funds.

“We’ve been a little bit stymied on the money trail,” one of them acknowledged Friday, explaining that at least several thousand dollars has been traced from a doctor in Germany to a New Jersey account held by Mohammed A. Salameh and Nidal Ayyad, the first two suspects arrested by the FBI.

In keeping with the investigative maxim that a crime can sometimes be solved by following a money trail, some federal officials said they had had high expectations that they might quickly be led beyond Germany to Iran or Iraq or to some recognized international terrorist group.

But so far, they have been unable to make any such connection and remain mystified about who may have sponsored the bombing three weeks ago that killed six people, injured more than 1,000 and crippled one of New York’s landmarks.

“Optimistically, it may be just a matter of time,” one top official said. “If the money came from an established organization or a country known to export terrorism, it naturally would want to hide it.”

This same official acknowledged that the explanation “could be” that the bombing was planned and executed by a group of local New York-New Jersey amateurs who acted alone, believing they were following the ideals of the radical cleric, Sheik Omar Abdul Rahman, whose New Jersey mosque the suspects had visited. The German doctor, the official continued, may simply have been a relative of Salameh who wanted to help.

“But I’m not ready to conclude that yet,” he said.

While reasons for the apparent investigative roadblock could not be learned, one source said that the FBI was attempting to bolster its inquiries overseas by subpoenaing records from several U.S. branches of foreign banks.

“We can’t get our hands on foreign banking records overseas unless officials of that country are willing to cooperate,” this source said. “But if a foreign bank has an American branch, we sure can obtain those particular records.”

He refused to provide any details or to comment on the pace of the investigative work.

Meanwhile, FBI court papers have revealed that a search of the New Jersey residence used by Ayyad, a chemical engineer, and by Bilal Alkaisi, the fifth and latest suspect, who surrendered this week, uncovered an explosive timing mechanism of a type used by terrorists.

But while the discovery of such a device might suggest involvement by a professional terrorist group, one federal official said that it does not rule out a home-grown plot.

Salameh, who has been accused of renting a van that delivered the estimated 1,000-pound bomb, has proclaimed his innocence, saying the van was stolen from him the evening before the Feb. 26 blast.

Robert E. Precht, his government-appointed defense lawyer, said that about $2,400 transferred into Salameh’s bank account was sent by a cousin in Germany to help pay medical expenses after Salameh was involved in an auto accident on Jan. 24.

Ayyad’s attorney, Leonard I. Weinglass, had another explanation. He said that Ayyad and Salameh kept a joint bank account for a wholesale candy business that they planned to start.

“Ayyad has gotten caught up in a Kafkaesque scenario,” Weinglass said. “Sure, he knew Salameh, but he had nothing to do with the bombing.”

The amounts of money transferred into bank accounts held jointly or separately by Salameh and Ayyad has not been disclosed by the FBI. But federal prosecutors said that more details about the alleged bombing conspiracy will be revealed next week in a larger superseding indictment against these two and others.

Some investigators have said privately they have uncovered several wire transfers from abroad of less than $10,000 each. While the amounts might seem paltry for any international terrorist group, the method of transfer suggests professional involvement to some investigators. Because banks are only required to report to the Treasury Department transfers of $10,000 or more, criminals often make transfers in smaller amounts.