A long-awaited report on the Fort Hood shooting faults the FBI for numerous failures in the run-up to the massacre that left 13 dead, concluding that agents' assessment of the gunman, Maj. Nidal Hasan, was "belated, incomplete and rushed" -- and suggesting political correctness played a role in the bureau's decision not to investigate him more thoroughly.

The report, obtained by Fox News Thursday afternoon, includes 18 specific recommendations for changes at the FBI. However, it does not recommend any disciplinary action against employees at the bureau.

The report found that the FBI "erred" in several respects -- by failing to interview Hasan when concerns were raised about his contact with known terrorist Anwar al-Awlaki; by failing to search for more email contact between Hasan and Awlaki, and by waiting too long to pursue leads on Hasan.

The FBI "erred in the process they followed to conclude that Hasan's communications with (Awlaki) were benign and acceptable," the report said. "Their assessment of Hasan was belated, incomplete and rushed, primarily because of their workload."

The report into the 2009 shooting was conducted over the course of two years by former FBI Director William Webster. The FBI had been under pressure from some lawmakers in recent days to release the document.

The Webster report found numerous problems in the way the FBI handled concerns about Hasan after he visited Awlaki's website in late 2008 and after he later sent messages to Awlaki -- who has since been killed in a drone strike in Yemen. Five months after the San Diego Field Office for the Joint Terrorism Task Force sent a lead to the Washington, D.C., office with concerns about Hasan, the report said, headquarters conducted their review, only to determine Hasan was not "involved in terrorist activities."

After the San Diego office complained, neither office took any additional action.

Among the concerns in the report was the decision by officials in Washington not to interview Hasan, which the report called "flawed." The report disputed officials' claims that interviewing him could have jeopardized the investigation, as well as his military career.

The report also quoted a San Diego official who claimed he suggested to headquarters in June 2009 that it would be appropriate to interview Hasan.

The Washington officer told him, according to a paraphrase in the report, that, "This is not (San Diego), it's D.C. and (the Washington office) doesn't go out and interview every Muslim guy who visits extremist websites."

The San Diego official also said he was told the subject was "politically sensitive."

The report repeatedly found that investigators did not fully research Hasan's background and files. The Washington office used a "limited" personnel file and in doing so uncovered documents praising his research on Islam, but not other Army records that raised other "issues" with him. The report faulted agents as well for not seeking additional correspondence between Hasan and Awlaki - though there were additional messages.

"The additional messages could have undermined the assumption that Hasan had contacted Awlaki simply to research Islam," the report said.

The report concludes that despite "missteps," the problems at the FBI in the lead-up to the massacre do not constitute "misconduct" that would warrant disciplinary action. It recommended a series of changes, to the way counterterrorism leads are handled, to the way it stores and shares data and to the way it trains officers.

Lawmakers had a mixed reaction to the report Thursday.

Sens. Joe Lieberman, I-Conn., and Susan Collins, R-Maine, the chairman and ranking Republican on the Senate Homeland Security Committee, said the report "reinforces" conclusions they had already reached about the "inadequacy" of the FBI probe.

But they added: "We are concerned that the report fails to address the specific cause for the Fort Hood attack, which is violent Islamist extremism. And we are skeptical that FBI analysts are now well-integrated into the FBI's operations, as the report states."

House Homeland Security Committee Chairman Peter King, R-N.Y., while not mentioning any omission on Islamic extremism, echoed the view that the report found "serious lapses" at the FBI. He praised the bureau for releasing the review to the public.

"The report is a stark reminder that the domestic radicalization by Al Qaeda and its affiliates is a serious threat to the homeland that absolutely must be addressed head-on by the federal government without concern for political correctness," he said.