DULUTH -- Police said Thursday that they have expanded the area they are searching for to find the Duluth woman who vanished two days ago after going out for an evening jog.

Jennifer Wilbanks, 32, was last seen in the downtown Duluth area at 8:30 p.m. Tuesday after leaving the house she shares with her fiance, police said. Wilbanks, an avid runner who once competed in the Boston marathon, was set to be married this weekend.

More Resources VIDEO: Ross Cavitt reports-Few Clues VIDEO: Ross Cavitt reports-Search VIDEO: 6 a.m. Police News Conference

At an 11 a.m. news conference, police Chief Randall Belcher said investigators have few clues in the woman's disappearance.

"At this point, we still have no indication that a crime has been committed," he said. "But we are treating it as a criminal investigation as of now."

At a 5:30 p.m. news conference Thursday, police said they have suspended the search by civilian volunteers but that canines and police would continue the effort for several more hours.

Belcher's comments came about five hours after another high-ranking official said police were going on the assumption that foul play was involved.

Maj. Don Woodruff said the FBI and the Georgia Bureau of Investigations have offered to assist local police in the probe, which is now focusing on the possibility that the woman was in harm's way.

"Based on the circumstances of the situation, we would now classify this as a criminal investigation," he said during a 6 a.m. news conference at police headdquarters.

Woodruff said there was no physical evidence in the case but detectives have concluded after speaking with relatives that the woman's disappearance was "totally uncharacteristic" of her behavior.

He said it was premature to classify anyone as a suspect in the case.

The case has garnered national attention, including segments on "Good Morning America," CNN, Court TV and Fox News. Wilbanks and her fiance were planning to tie the knot Saturday at Duluth First United Methodist Church in a ceremony said to include 14 bridesmaids and 600 guests.

Wilbanks was last seen wearing a gray sweat shirt and blue sweat pants. She stands 5 feet 8 inches tall and weighs about 120 pounds, police said. She has brown hair and brown eyes.

Anyone with information was asked to call Duluth police at 770-476-4151.

John Mason, the woman's fiance, said he called police after she failed to return home, and he and other relatives were unable to find her.

"She left out of here with a radio and just the clothes she had on," Mason said, adding that he doesn't believe the prospective bride was suffering from last-minute pre-wedding jitters. "If it's cold feet, it's the worst case of cold feet I've seen."

Joyce Parrish, the woman's mother, said she was excited as the wedding day neared. Parrish said her daughter was putting the final touches on her wedding plans. She said they talked just a few hours before she disappeared.

Up to 250 volunteers handed out fliers to motorists Wednesday that sought help from anyone who might have information about the woman's disappearance.

Police used dogs to search the area, and divers from the the state Department of Natural Resources searched the banks of the nearby Chattahoochee River.

Belcher said Thursday that police plan to expand the area they are searching for by scouring places where she might have gone running.

"We are going to extend the search area out from where we searched yesterday," he said.

Mason's father, Claude Mason, is a former Duluth mayor and municipal judge.

wsbtv.com Staff Writer Alfred Charles and Channel 2 Action News reporter Ross Cavitt contributed to this report.