South Carolina authorities have focused their search on an area just south of where teenager Brittanee Drexel disappeared after discovering the last place her cell phone gave off a signal.

Georgetown County Sheriff Lane Cribb said police spent a second day combing a river and highway 35 miles south of Myrtle Beach, where the upstate New York 17-year-old was vacationing on spring break.

Searchers using dogs, helicopters and boats concentrated Saturday on a 7-mile area along the South Santee River and U.S. 17.

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Drexel's cell phone signal was captured last Sunday, a day after police say the teen was last seen.

Myrtle Beach Capt. David Knipes told reporters Sunday that "there will only be a handful of officers doing some final things associated with that search."

Knipes said the search hasn't yielded any new clues in the case.

Drexel, a junior at Gates-Chili High School in Rochester, N.Y., left the Bar Harbor Hotel at about 8 p.m. on April 25 to visit a friend named Peter Broswick, who was with a group of male friends at the nearby Blue Water Resort. Police have released footage of the girl entering and leaving the lobby of the Blue Water about 8:30 p.m.

Detectives think Broswick may have been the last one to see the missing teen alive.

Broswick, who is also from Rochester, left Myrtle Beach to return home about 1 a.m. the night Drexel was last seen, according to News Channel 15's CarolinaLive.com.

Knipes told FOXNews.com he doesn't know the nature of the pair's relationship, and he wouldn't call Broswick a suspect.

Drexel's mother, Dawn Drexel, said she is concerned because the teen suffers from depression. The girl may have been upset because she and her husband are getting divorced, Drexel said.

Dawn Drexel added that she didn't want her daughter to go to Myrtle Beach, but the girl had "her mind set" on it and went any way. They continued to keep touch by phone — until the contact ended abruptly the night Brittannee disappeared.

Family and friends spent the past week canvassing popular beach clubs and hangouts in the resort town without any results.

Brittanee Drexel has blue eyes and shoulder-length brown hair with blond highlights. She's 5 feet tall, weighs about 100 pounds and was last seen wearing a multi-colored shirt, black shorts and flip-flops.

Those with any information are asked to call Myrtle Beach Police at (843) 918-1300, 1-800-CRIME-TV or 1-800-THE-LOST (843-5678).

Click here to visit HelpFindBrittanee.com.

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The Associated Press contributed to this report.