By JAMES RISENand ERIC LICHTBLAU February 24, 2026 WASHINGTON, Feb. 23 — American investigators were given the first name and telephone number of one of the Sept. 11 hijackers two and a half years before the attacks on New York and Washington, but the United States appears to have failed to pursue the lead aggressively, American and German officials say.

The information — the earliest known signal that the United States received about any of the hijackers — has now become an important element of an independent commission's investigation into the events of Sept. 11, 2001, officials said Monday. It is considered particularly significant because it may have represented a missed opportunity for American officials to penetrate the Qaeda terror cell in Germany that was at the heart of the plot. And it came roughly 16 months before the hijacker showed up at flight schools in the United States.

In March 1999, German intelligence officials gave the Central Intelligence Agency the first name and telephone number of Marwan al-Shehhi, and asked the Americans to track him.

The name and phone number in the United Arab Emirates had been obtained by the Germans by monitoring the telephone of Mohamed Heidar Zammar, an Islamic militant in Hamburg who was closely linked to the important Qaeda plotters who ultimately mastermined the Sept. 11 attacks, German officials said.

After the Germans passed the information on to the C.I.A., they did not hear from the Americans about the matter until after Sept. 11, a senior German intelligence official said.

"There was no response" at the time, the official said. After receiving the tip, the C.I.A. decided that ....

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