Homeland Security Secretary Michael Chertoff says measures, such as hiring more agents and installing hi-tech detectors, have resulted in 22 percent decrease in arrests of illegal immigrants along the southern U.S border with Mexico. He says this is a sign U.S. authorities are beginning to get control of the border. But a separate U.S. government audit released this week found that thousands of illegal migrants made their way undetected through screening procedures at legal ports of entry, such as airports and land border crossings. VOA's Cindy Saine reports from Washington.

Over the past year, the Bush administration has stepped up raids on companies that employ undocumented workers, hired more border control agents, built fences and installed high-tech security devices along the southwestern border.

Homeland Security Secretary Chertoff says the tougher enforcement measures have led to more than a 20 percent drop in border arrests. "We are beginning to see a significant turn in the direction of migration. We haven't completed the job yet, but we've made a significant first step and are reversing the tide of illegal migration between the ports of entry," he said.

Demetrios Papademetriou, president of the Migration Policy Institute, an independent, non-partisan research group based in Washington, agrees that real progress has been made in border security, but thinks only time will tell if the gains are lasting.

"To take this progress and say that we're turning the tide is certainly an overstatement. There have been many times in the past 20 years or so that politicians have made similar claims, and six months later, a year later, you know, things turned again," he said.

Secretary Chertoff said that arrests in the interior of the United States were up substantially during fiscal year 2007, with criminal charges filed against 863 people, up from 716 the year before.

Despite the progress, a government audit released earlier this week found that thousands of illegal workers came in undetected through legal entry points, such as airports and land border crossings. The Government Accountability Office said weaknesses in U.S. Customs and Border Protection operations increase the potential that terrorists and criminals could enter the country. Auditors said they found border patrol officers suffered from morale problems, fatigue and lack of backup.

A Customs and Border Protection official acknowledged staffing shortages, but doubted that the agency had failed to catch thousands of violators.

Migration expert Demetrio Papademetrious downplayed the importance of the GAO audit report. "I tend to actually discount this particular study. There is a "gotcha" element to it, which of course captured headlines. But the fact remains that every time that you test these processes, individuals, sometimes in large numbers, will actually be able to pass through the system. In other words, there is no such thing as a hermetically-sealed border enforcement effort. There will never be such an effort. Not at the borders, not on airlines, not anywhere else," he said.

Some 400 million people cross U.S. borders each year, and authorities have been unable to screen all of them without disrupting U.S. travel and trade with Canada and Mexico.