DULUTH, Minn. (AP) _ A man believed to be escaped murderer Bernard Welch has been spotted in Minnesota, a federal official says, and the nationwide search now is based in Duluth.

Welch, 45, serving a 144-year sentence for burglary and the murder of Dr. Michael Halberstam in 1980, escaped from a corrections center in Chicago on May 14. He was joined in the escape by Hugh Colomb, 31, who was serving a 48- year sentence for robbery and murder.

Robert C. Leschorn of the U.S. Marshals Service, who is coordinating the search, wouldn't say Thursday where Welch reportedly was seen.

''There's always the chance he's in the area,'' Leschorn said.

Leschorn released an artist's sketch showing how Welch may look now. Investigators believe he has altered his hair style and may be wearing horn- rimmed glasses.

Welch bought a home in Duluth in 1978 and lived there with a local woman.

Leschorn said it is believed that Welch and Colomb are still together.

He and Colomb, 31, broke through a concrete wall and slid down a 75-foot extension cord from the downtown Chicago corrections center.

Welch was interrupted by Halberstam while he was burglarizing the doctor's home in Washington, D.C. Halberstam, who was shot by Welch, ran Welch down with his car on the way to the hospital, where the doctor later died.

Authorities said Colomb can be recognized by a tattoo of a man and woman which covers his back, and by his habit of biting his fingernails very short.

Leschorn stressed that both Welch and Colomb are ''avid outdoorsmen, very good in the woods.'' Both also have been described as dangerous.

Chester Lonczak of the U.S. Forest Service said Forest Service employees have been instructed to look out for suspicious campers.