"We can't imagine why getting information is being treated like the plague," the engineer wrote in one of a number of e-mails released Friday that describe greater concerns about Columbia's safety in the days before its breakup.

Other documents NASA released show that Columbia may have been struck by as many as three large chunks of foam that smashed against delicate insulating tiles as it took off, not just the one previously acknowledged.

Robert Daugherty, an engineer at NASA's Langley research facility in Hampton, Va., did not indicate that he believed the breach would cause Columbia to break apart during its fiery descent. "No way to know, of course," he wrote.

But Daugherty warned in his e-mail on Jan. 29 about a possible breach near the seal of Columbia's wheel compartment that could have been caused by damage to the shuttle's thermal tiles there. He seemed mostly worried about the risks of pilots struggling to land Columbia with one or more tires damaged by extreme heat.

"It seems to me that if mission operations were to see both tire pressure indicators go to zero during entry, they would sure as hell want to know whether they should land with gear up, try to deploy the gear or go bailout," Daugherty wrote.

Senior NASA officials have steadfastly supported assurances by The Boeing Co., a contractor, since the accident that Columbia was expected to be able to return safely despite possible tile damage along its left wing. They also have maintained that concerns expressed in e-mails among midlevel engineers such as Daugherty were part of a "what-if" analysis, and that even these engineers were satisfied with Boeing's conclusions.

"During the flight, no one involved in the analysis or the management team or the flight team raised any concerns," NASA spokesman James Hartsfield said Friday.

But the e-mails disclosed in Washington raise questions about the assurances by Boeing, including underlying assumptions about the likelihood of damage from a large chunk of breakaway foam and whether damage to Columbia might have been caused by falling ice.

The e-mails also include references by Daugherty and another Langley employee, Mark J. Shuart, about secrecy within NASA about the study of risks to Columbia. Shuart wrote Jan. 28 to two other employees, referring to the foam strike, "I am advised that the fact that this incident occurred is not being widely discussed."

The e-mails, which never were passed to senior mission controllers in Houston during Columbia's flight, will be turned over to the board investigating the accident, board spokeswoman Laura Brown said. All seven astronauts died in the breakup Feb. 1.

The e-mails had been sought since last week by news organizations under the Freedom of Information Act. Employees at NASA's headquarters here published them Friday with little fanfare on the agency's Web site.

Among the e-mails were two written after the breakup. Daniel D. Mazanek of the Spacecraft and Sensors Branch at Langley wrote Feb. 7 that the debris that struck Columbia might have been ice, not foam from the external fuel tank.

Boeing had calculated that a chunk of foam weighing 2.67 pounds was responsible. But Mazanek estimated that a chunk of ice the same size would have been more damaging because it would weigh 63.4 pounds, "the equivalent of a 500-pound safe hitting the wing at 365 mph."

Last week, NASA disclosed a similar e-mail by Daugherty. He wrote two days before Columbia's breakup about risks to the shuttle from "catastrophic" failures caused by tires possibly bursting inside the wheel compartment from extreme heat.

Daugherty was responding in that e-mail to a telephone call Jan. 27 from officials at the Johnson Space Center asking what might happen if Columbia's tires were not inflated when it attempted to land.

Daugherty cautioned in the e-mail disclosed earlier that damage to delicate tiles near Columbia's landing gear door could permit dangerous temperatures causing one or more tires to burst, perhaps ending with failures that would place the astronauts "in a world of hurt."

In other documents released Friday, a report by Boeing employees said that cameras saw three large pieces of debris, each up to 20 inches long, that shattered into a shower of particles after striking Columbia along its left wing. The report, among those supporting Boeing's assurances to NASA that Columbia could return safely, was dated eight days before the spacecraft broke apart over Texas.

Earlier Boeing reports during Columbia's flight had focused on possible damage from "a large piece of debris," also about 20 inches.

NASA released three reports analyzing possible damage to Columbia's insulating tiles. News organizations had previously obtained two of these. The third, dated Jan. 24, indicated the highest risk of damage was along the leading edge of Columbia's left wing, based on the speed and on the angle of the strike as the shuttle roared skyward.

The accident board investigating the disaster has said previously that Columbia almost certainly suffered a devastating breach along its wing and possibly its wheel compartment that allowed searing air to seep inside the shuttle during its descent at nearly 12,500 miles per hour.

Unusual temperature readings inside the wing began to occur within minutes of its re-entry, far off the coast of California.