Volunteer divers on Sunday called off a seven-hour search of the cold, dark Schuylkill near where Shane Montgomery was last seen without discovering any new signs of the 21-year-old college student.

Just a week ago, the divers, from the Garden State Underwater Recovery Unit, discovered Montgomery's keys in the water near the riverbank just south of Kildare's Irish Pub in Manayunk. Montgomery had been partying there with friends before he disappeared early Thanksgiving Day.

Family members are now trying to figure out their next step.

"It's tough," Montgomery's uncle Kevin Verbrugghe said as relatives embraced on the deck of the Manayunk Brewing Co.

Verbrugghe had hoped Sunday would be the last day of the search.

Montgomery was last spotted leaving Kildare's on Main Street early Thanksgiving Day, and police later recovered video that showed him on a footbridge crossing the Manayunk Canal that leads to a parking lot across the street from the bar.

Last week, divers discovered Montgomery's keys just south of that lot.

On Sunday, up to eight volunteer divers centered their search on that area, said Greg MacTye, captain of the recovery unit.

The divers, working in shifts, slowly combed the murky brown waters as two small boats floated on the Schuylkill above.

The Philadelphia Police Marine Unit was also on hand in case the divers found anything, a law enforcement officer said.

MacTye said that divers were searching about a quarter-mile stretch of the river and that visibility was about four feet in any direction, conditions he described as "not bad."

The search posed a challenge because there was no eyewitness who could pinpoint where Montgomery might have fallen in, MacTye said.

"If I can get an eyewitness," he said, "I can usually find them."

In the initial days of the search for Montgomery, a law enforcement source said, the Police Department Marine Unit used a number of methods to try to isolate the area where the student might have fallen in, from sonar devices to cadaver dogs on boats.

Those efforts were unsuccessful, the source said.

The volunteer dive team has since been focusing its efforts based on the last sighting of Montgomery and last week's discovery of his keys.

A handful of family members and close friends watched Sunday from the riverbank as divers searched for clues.

Despite the lack of success, Verbrugghe remained optimistic his nephew would eventually be found.

"We're not going to lose this fight," he said.

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Inquirer staff writer Mike Newall contributed to this article.