WASHINGTON — The Bush administration partially lifted the veil of secrecy today surrounding an investigation into deadly anthrax mailings in 2001, presenting details to families of the victims after a federal judge ordered the release of voluminous records.

Two officials said the FBI was ready to end its probe of the case, one week after the suicide of Bruce Ivins, a brilliant but troubled government microbiologist who investigators say was behind the attacks. The officials spoke on condition of anonymity, saying they were not authorized to talk about the sensitive case.

U.S. District Judge Royce Lamberth ordered the release of hundreds of pages of documents, including more than a dozen search warrants issued as the government closed in on Ivins in an investigation into events that killed five, sickened dozens and rattled the nation a few weeks after the Sept. 11, 2001 terror attacks.

The long-sealed material was expected to be available to the public within hours.

Lamberth ordered the release after consultation with Amy Jeffress, a national security prosecutor at the Department of Justice.

Separately, families of victims of the anthrax mailings were ushered into a briefing at FBI headquarters, several blocks from the courthouse.

The events in Washington unfolded as a memorial service was held for Ivins at Fort Detrick, Md., the secret government installation in Frederick, Md., where he worked. Reporters were barred.

The investigation dates to 2001, when anthrax-laced mail turned up in two Senate offices as well as news media offices and elsewhere. At the time, the events were widely viewed as the work of terrorists, and delivery of mail was crippled when anthrax spores were discovered in mailing equipment that had processed the contaminated envelopes.

The papers ordered unsealed were expected to reveal how the FBI narrowed the scope of its investigation to the Fort Detrick scientist.

The evidence that Lamberth authorized to be made public also may to answer other questions in the investigation that dragged on for years, tarnishing the reputation of the FBI in the process.

The government recently paid $6 million to settle a lawsuit by Stephen A. Hatfill, whose career as a bioscientist was ruined after then-Attorney General John Ashcroft named him a “person of interest” in the probe.

The briefing for victims and their survivors came eight days after Ivins killed himself as prosecutors prepared to charge him with murder.

Ivins’ lawyer has maintained that the 62-year-old scientist would have been proved innocent had he lived. And some of Ivins’ friends and former co-workers at the Fort Detrick biological warfare lab say they doubt he could or would have unleashed the deadly toxin.

The Justice Department “has a legal and moral obligation to make official statements first to the victims and their families, then the public,” Attorney General Michael Mukasey said Tuesday.

Officially, the case will stay open for an undetermined but short period of time. That will allow the government to complete several legal and investigatory matters that need to be wrapped up before it can be closed, the officials said.

The records could shed light on numerous elements of the case. Among the matters still in question:

—An advanced DNA analysis matched the anthrax used in the attacks to a specific batch controlled by Ivins. It is unclear, however, how the FBI eliminated as suspects others in the lab who had access to it.

—Ivins’ purported motive — sending the anthrax in a twisted effort to test a cure for it, according to authorities. Ivins complained of the limitations of animal testing and shared in a patent for an anthrax vaccine. No evidence has been revealed so far to bolster that theory.

—Why Ivins would have mailed the deadly letters from Princeton, N.J., a seven-hour round trip from his home. In perhaps the strangest explanation to emerge in the case so far, authorities said Ivins had been obsessed with the sorority Kappa Kappa Gamma for more than 30 years. The letters were sent from a mailbox down the street from the sorority’s office, which is across the street from Princeton University.

Investigators can’t place Ivins in Princeton but say the evidence will show he had disturbing attitudes toward women. Other haunting details about Ivins’ mental health have emerged, and his therapist described him as having a history of homicidal and sociopathic thoughts.