Guards for the security company were involved in a shooting in September that left at least 17 Iraqis dead at a Baghdad intersection. Outrage over the killings prompted the Iraqi government to demand Blackwater’s ouster from the country, and led to a criminal investigation by the F.B.I., a series of internal investigations by the State Department and the Pentagon, and high-profile Congressional hearings.

But after an intense public and private lobbying campaign, Blackwater appears to be back to business as usual.

The State Department has just renewed its contract to provide security for American diplomats in Iraq for at least another year. Threats by the Iraqi government to strip Western contractors of their immunity from Iraqi law have gone nowhere. No charges have been brought in the United States against any Blackwater guard in the September shooting, either, and the F.B.I. agents in Baghdad charged with investigating whether Blackwater guards have committed any crimes under United States law are sometimes protected as they travel through Baghdad by Blackwater guards.

The chief reason for the company’s survival? State Department officials said Friday that they did not believe they had any alternative to Blackwater, which supplies about 800 guards to the department to provide security for diplomats in Baghdad. Officials say only three companies in the world meet their requirements for protective services in Iraq, and the other two do not have the capability to take on Blackwater’s role in Baghdad. After the shooting in September, the State Department did not even open talks with the other two companies, DynCorp International and Triple Canopy, to see if they could take over from Blackwater, which is based in North Carolina.

“We cannot operate without private security firms in Iraq,” said Patrick F. Kennedy, the under secretary of state for management. “If the contractors were removed, we would have to leave Iraq.”

Still, serious risks remain for Blackwater and at least some of its current and former personnel. A federal grand jury continues to consider evidence in the Baghdad shooting. Although the company is not likely to face any criminal charges, people involved in the case say that some Blackwater guards involved in the shooting are cooperating with the F.B.I. as it pursues evidence against other guards.

Separately, a former Blackwater guard is under criminal investigation for the December 2006 shooting death of an Iraqi guard for an Iraqi vice president, and may soon face federal charges. In a third case, two former Blackwater workers pleaded guilty to weapons-related charges, but both received sentences that included no jail time in return for their cooperation with federal prosecutors in a broader investigation.

A House committee has also asked the Internal Revenue Service to begin an inquiry into whether Blackwater has designated its guards as independent contractors rather than employees to in order to avoid paying and withholding federal taxes. The State Department renewed the security contract for only one year — just long enough to take the company into the start of the next administration. And Blackwater’s political connections to the Bush administration may not serve it well if the Democrats win the White House in November.

Given the furor that surrounded Blackwater after the September shooting in Baghdad, critics say the decision to renew the company’s contract in Iraq is a sign of the Bush administration’s inability to curb its reliance on outside contractors in the war.

“The shooting incident was like a hammer blow, but where are the consequences?” said Peter W. Singer, a scholar at the Brookings Institute and author of “Corporate Warriors,” a book about contractors in Iraq. “I think it points to the fact that the dependence on contractors is like a drug addiction. They just can’t help themselves.”

Representative Henry Waxman, California Democrat who is chairman of the House Oversight and Government Reform Committee, which has been investigating Blackwater on several fronts, said, “I can’t understand why Blackwater’s contract was renewed. It seems to me the administration should have looked for others who could do the job, including the U.S. military.”