Struggling with a deluge in passport applications, the State Department did what much of the government does to deal with a manpower crunch: It hired more private contractors.

But the practice of outsourcing allowed hired hands to snoop around in presidential candidates' files. And now it's pointing to questions about whether outside contractors should have access to such sensitive information about any citizen.

The nation has needed to use nongovernment workers as well as federal employees from its earliest days, Rep. Solomon Ortiz, D-Texas, said this month in a congressional hearing that focused on military contracting.

But he asked, "Have we gone too far in recent years by perhaps relying too much on contractors?"

The government routinely relies on private firms to do sensitive work -- from managing weapons systems to protecting traveling diplomats to helping maintain records that contain private information on U.S. citizens. The Bush administration in particular has embraced the practice of outsourcing as a way to save money and improve efficiency, particularly in Iraq where there are just as many defense contractors as there are service members.

With the influx of contractors come increasing questions about lack of control.

The State Department, for example, has had to defend its employment of private security guards after several Blackwater Worldwide employees were involved in shootings that left Iraqis dead.

Then, last week, contractors were found to have pried into the passport files of Democratic presidential candidate Barack Obama and Republican rival John McCain. Two contractors were fired and a third disciplined.

Democrat Hillary Rodham Clinton's files also were breached when a State Department worker used the senator's name during a training session and was reprimanded, officials said. The worker was a government employee and not a contractor.

The State Department's inspector general is expected to determine whether the files of other high-profile people were breached and if the searches involving the presidential candidates were politically motivated.

Spokesman Sean McCormack said Monday that the Justice Department has an "open invitation" to become involved. Attorney General Michael Mukasey has indicated that prosecutors are likely to wait until the assessment concludes before deciding whether to open an investigation of their own.

In the meantime, McCormack said the agency isn't concerned it might be relying too much on private firms to help issue passports. The State Department's Office of Passport Services employs about 2,600 contractors nationwide.

"These contractors go through vigorous personal integrity tests, the same kinds of tests that career government employees undergo," he said.

"They are an essential part of what we do here at the State Department in terms of providing services to the American people, and they're an essential part of the U.S. government providing the kinds of services that the American people expect their government to provide," McCormack said.

Last year, the number of passport application requests soared after the January implementation of new rules that required air travelers from Canada, Mexico, the Caribbean and Bermuda to present passports. The State Department went from issuing some 12 million passports in 2006 to 18 million in 2007.

As the backlog worsened, the State Department took drastic and expensive measures, even paying some employees to return to the U.S. from overseas to help handle the paperwork. Anticipating the influx of requests to continue, the department hired contractors too.

"In order to deal with 18 million passports a year, we require lots of people to have access because it's compartmentalized in the sense that different people perform different functions, including recording if someone advises that their passport has been lost or stolen," said Undersecretary Patrick Kennedy, the department's top management officer.

It remains unclear as to exactly what the contractors might have seen. Passport applications typically contain only basic personal information such as name, citizenship, age, Social Security number and place of birth. The files generally would not list countries the person has traveled to, agency officials said.

However, Passport Services maintain other records too, according to a Jan. 9 notice in the Federal Register. The federal notice says such information as marriages overseas, court orders, arrest warrants and medical and financial reports may also be contained within the system.

Further, outside "users" -- including other government agencies and foreign governments -- may be given certain information. In the case of foreign governments, the data would be shared primarily to aid in law enforcement, immigration and fraud prevention, the notice states.

In a statement released late Monday, the State Department said extraneous information would be included in passport application files only under rare circumstances, such as suspected fraud.

Also, foreign governments are not given access to the U.S. electronic system that contains the files, the agency noted.

"During travel, a U.S. passport number is checked against our list of invalid travel documents to ensure the traveler is not using an invalid document," according to the State Department. "Foreign governments query our data and we confirm whether the document has been reported lost or stolen or is otherwise invalid."

There are about 180 million to 200 million records in the passport system.

The two companies that provided the workers for the State Department -- Stanley Inc., of Arlington, Va., and The Analysis Corp., or TAC, of McLean, Va. -- have said their employees' actions were unauthorized and not consistent with company policies.