ROUND ROCK, Texas – New Mexico Gov. Bill Richardson on Friday touted his varied government experience but admitted there's one matter he's never gotten to the bottom of: the Roswell UFO mystery.

During a campaign stop at a Dell Inc. town hall meeting, an employee asked Mr. Richardson to pledge that if he's elected president he will release the Roswell files.

The 1947 incident in the New Mexico desert remains largely classified.

The U.S. military says it involved the wreckage of a top-secret research balloon. But the secrecy surrounding the episode has spawned a cottage industry of UFO buffs who maintain space aliens and their ship were captured and hidden away.

Mr. Richardson acknowledged Friday that the matter has remained a mystery to him.

"I remember I had my constituents ask me. I was the congressman and I said, 'Well, Department of Defense, Los Alamos labs, what is this? What is the data you have?' " he said.

"Oh, it's classified" was the response, he said. "That ticked me off."

The Roswell question sparked laughter from about 200 Dell employees. But the New Mexico Democrat, who seeks to win his party's nomination for the White House, used the query to discuss the larger issue of government secrecy.

"I've been in government. I've been in the cabinet. I've been in the Congress," he said. "And I've always felt the government doesn't tell the truth as much as it should on a lot of issues."

As for whether Roswell was home to a secret CIA extraterrestrial liaison program, Mr. Richardson promised to consider opening the files if he makes it to the White House.

"Sure," he said with a broad grin. "I'll work with you on that."

Mr. Richardson was in the Austin area for a fundraiser and a campaign stop at the Dell computer company headquarters.

During the town hall meeting, Mr. Richardson addressed another issue – illegal immigration.

He said he supports doubling the size of the Border Patrol and increasing high-tech detection equipment along the U.S.-Mexico border. But he dismissed calls to build a wall.

"The wall makes no sense. None whatsoever," he said. "You have a 12-foot wall and you know what's next? A 13-foot ladder."

Moreover, he added, "it's not a good symbol between countries."