Fixing cybersecurity problems in the U.S. is a top priority at the U.S. Department of Homeland Security, said the agency's leader, but lawmakers didn't focus on the issue during a hearing in Congress Wednesday.

Cybersecurity is a "very big issue" that DHS remains concerned about, said DHS Secretary Michael Chertoff, testifying before the House of Representatives Homeland Security Committee. Chertoff didn't go into details because much of the department's cybersecurity efforts are classified, he said.

"I can assure you that we are working with other elements of the federal government and giving highest priority an enhanced strategy with respect to cybersecurity," he said. Cybersecurity threats have "enormous potential to do damage to the United States in years to come," Chertoff added.

Chertoff testified before the committee in a hearing titled, "Holding the Department of Homeland Security Accountable for Security Gaps." But while cybersecurity problems continue inside and outside of the U.S. government, lawmakers focused on other issues during the hearing, including the hiring of border agents, training of bomb-sniffer dogs, and the scanning of airline cargo.

Just this week, the U.S. Department of Defense acknowledged a successful attack on an unclassified e-mail system earlier this year.

While not focusing on cybersecurity, committee chairman Bennie Thompson, a Mississippi Democrat, said DHS needs to improve in several areas. Thompson has criticized the department's cybersecurity efforts in the past, but cybersecurity issues were not on Thompson's list of top priorities for Chertoff in the remaining 16 months of U.S. President George Bush's administration.

Instead, Thompson called on Chertoff to fill vacancies at DHS, to finish regulations for container security at ports, and to implement a biometric air passenger screening program.

"We owe the American people security," Thompson said. "We owe them accountability. And most importantly, we owe them freedom from fear."

Other than the short Chertoff statement on cybersecurity, the issue did not come up again in the first 90 minutes of questions from lawmakers. Representative Jim Langevin, a Rhode Island Democrat, questioned Chertoff about alleged cyberattacks by Chinese hackers after more than two and a half hours of other questions. Representative Mike Rogers, an Alabama Republican, used part of his question time to complain to Chertoff that many bomb-sniffing dogs used by DHS came from overseas.

Rogers urged Chertoff to find ways to breed bomb-sniffing and cadaver dogs in the U.S. "I'm concerned that we are increasingly relying on foreign imported dogs," he said.