Gunfire rattled around the streets adjacent to the New Orleans Veterans Affairs Medical Center, where James E. Aldridge found himself stationed a week after Hurricane Katrina hit.

As the city descended into chaos and many people were still attempting to flee, Aldridge and 33 other members of the U.S. Veterans Affairs Department police force were just reporting for duty.

Their orders: to secure the medical center and fend off looters prepared to wade through the six feet of murky, diseased water in search of booty.

Located just one block north of the Superdome, the officers found themselves in one of the most dangerous areas of the city, with no one to call for backup. In those lawless days before the arrival of the 82nd Airborne Division, Aldridge had been informed that all the city's law enforcement personnel were pulled out each day at dusk. "When we got there on Sunday, it didn't seem like a major American city. It seemed like a war zone," said Aldridge.

But though many would go a long way to avoid working in such conditions, Aldridge volunteered for exactly this sort of duty.

It is a world away from his regular duties at the VA health care center in Orlando. It is nothing like his previous volunteer work as a federal employee: helping police the 2002 Winter Olympics in Salt Lake City. But when the call for help went out, he felt duty-bound to offer his assistance.

"I decided to volunteer because I'm a police officer and we could see what was needed. The agency was requesting volunteers."

Aldridge is not alone.

There are 1,674 employees of the Interior Department and more than 1,000 members of the Public Health Service Commissioned Corps -- to name just two agencies -- deployed in the hurricane areas. This pattern is repeated across the government, with agencies sending between 10 and 1,000 employees to take part in Katrina duty, demonstrating a federal response that stretches far beyond the Federal Emergency Management Agency and the Department of Homeland Security. That will continue: With Hurricane Rita approaching, several Washington-based public health service officers yesterday said they are being sent to Texas.

The federal workers come from all parts of the country, with myriad skills. Among the 238 VA employees currently deployed along the Gulf Coast are health professionals, secretaries and housekeeping staff, in addition to VA police officers such as Aldridge.

There is no total figure for how many federal workers are involved at this stage, however. Although all their work is being coordinated by FEMA, the agency says it has no way of counting heads.

Some are there to provide backup to beleaguered state services, such as those from the Education Department, which has 50 volunteers along the Gulf.

Others have more unique roles, such as the 22 workers from the State Department and the U.S. Agency for International Development, whose function is to help representatives of foreign embassies obtain access to the affected region, identify and recover the dead, and brief foreign media.

"In the final analysis, Katrina is likely to mean the largest peacetime domestic mobilization in the history of the United States," said David M. Walker, U.S. comptroller general and head of the Government Accountability Office.

The impact of Katrina will be felt throughout the federal government, he added. "There's no question there will be a ripple effect. How much will depend on the various departments and agencies."

Walker, who will work with the federal departments' inspectors general, as well as state, city and county auditors, to evaluate the success of the federal response, cautioned against agencies throwing too much manpower into the region. "There are many people who want to help at some point of time, but there has to be some organization to ensure they are effectively utilized," he said.

This has become somewhat irrelevant for thousands of federal workers who have volunteered to help but have been denied permission to go by managers.

At the Department of Housing and Urban Development, for example, approximately 700 employees signed up, but only 40 were sent. Charles Showalter of the American Federation of Government Employees estimates that "many hundreds, if not thousands," have been held back.

He said the government has been uneven in deciding who goes. "Some officers were forced into deployment, yet it appears other officers of a similar specialty [who did volunteer] were bypassed. I have received reports from many of my local presidents saying that far more people are putting themselves forward than are being put on the [deployment] list," Showalter said.

Last week, employees at the Department of Homeland Security were sent an e-mail thanking them for their offers of "personal sacrifices" but advising that there were many restrictions on those who could participate -- for instance, only employees with government credit cards would be allowed to go. The e-mail suggested that employees wanting to help should instead contribute to the American Red Cross and other relief organizations.

Walker is already evaluating the performance of agencies in the days and weeks after the hurricane made landfall.

"The Coast Guard appears to have performed well, the Weather Service did well, the Postal Service took a number of steps to try and minimize disruption," Walker said. "The military seems to have responded quickly after they were called out, but there was a delay, and FEMA and others are not looking like they did so well."

James Aldridge, normally stationed in Orlando, stands guard against looting at the New Orleans VA Medical Center.