An elite panel of scientists urged the federal government yesterday to take a deeper look at the safety of a controversial research laboratory being built by Boston University.

The recommendation comes from the National Research Council, an independent advisory board, which sharply criticized the federal government in November for previous safety reviews of the BU project, branding them "not sound and credible."

If the federal government heeds the advice, the opening of the BU lab could be significantly delayed. Already, the university has abandoned long-stated plans to open the South End facility by this fall, and a BU spokeswoman said yesterday that it was premature to speculate about a revised opening date for the $200 million project.

One of the scientists who drafted the recommendations, Gigi Kwik Gronvall of the University of Pittsburgh, said that the panel did not consider how long it would take to conduct the expanded review. "I know this is a dissatisfying answer, but it was not part of our charge to do that," Gronvall said in an interview.

BU won a competition in 2003 to open one of two new Biosafety Level-4 labs in the country, regarded as cornerstones in the Bush administration's campaign to prepare for possible acts of bioterrorism. The high-security lab, being built on the BU medical school campus, would allow scientists to work with the world's deadliest germs, including those that cause Ebola, plague, and Marburg.

Opponents of the project, which is largely underwritten by the National Institutes of Health, have taken to the streets and the courts for five years to fight the lab. While state and federal judges did not halt construction, now 80 percent complete, they did order further review of its risks.

Clearly stung by the National Research Council's November rebuke, NIH director Elias A. Zerhouni commissioned a blue-ribbon panel to conduct a new safety analysis of the lab.

Zerhouni also sought the council's guidance on how that review should be conducted, which arrived yesterday in the form of a 21-page letter. The council stressed its belief that Biosafety Level-4 labs are needed and that they can be operated safely in urban areas.

"However," the letter said, "the committee's view remains that the selection of sites for high-containment laboratories should be supported by detailed analyses and transparent communication of the available scientific information regarding possible risks."

The council recommended that NIH perform a far more detailed analysis of the risk of lethal germs leaking into the lab's surrounding neighborhood. And it said the review should include more types of germs than the earlier NIH analysis. Federal scientists should also take into account not only work done in the Biosafety Level-4 lab, but also research conducted in lower-security labs that will operate in the project.

The council emphasized that NIH should carefully weigh the project's impact on the South End, an economically and ethnically diverse neighborhood with a significant proportion of poor residents.

"Communities, such as the . . . neighborhoods that surround the [project], face challenges that could affect, among other things, the transmission of infectious disease, the health consequences, and the scope and deployment of public health responses," the council said.

Zerhouni did not respond to a request to comment on the recommendations.

Eloise P. Lawrence, a Conservation Law Foundation lawyer representing lab opponents, hailed the call for a comprehensive review.

"That sounds like it's squarely on what the community has been saying for years: There may be greater risk to placing this laboratory into this particular location, and that should be factored in," Lawrence said.

But one of the lab's most ardent opponents, Mel King, a former member of the Boston City Council, said that after five years, the project has been subjected to enough review.