The U.S. Coast Guard suspended its search for missing kayaker Samantha Youngs off the La Jolla coast Tuesday, Oct. 13, after crews searched 484 square miles of ocean and found no sign of her.

Youngs, 27, last contacted family just before 8 p.m. Monday, Oct. 12, while paddling a blue kayak near Black's Beach, according to a San Diego Police Department missing-person alert. She was possibly last known to be in the area of 2800 Torrey Pines Scenic Drive, Times of San Diego reported. Her car was found at the Torrey Pines Gliderport cliffside parking lot.

Her family reported her missing, and watchstanders at Coast Guard Sector San Diego received the notification at 6 a.m. Tuesday, according to a Coast Guard press release. SDPD classified Youngs as "at risk" in its alert.

Crews from Coast Guard Station San Diego and Air Station Ventura responded between 7:15 and 7:30 a.m., Coast Guard spokesman Petty Officer 3rd Class Charlie Valor told NBC San Diego. The Coast Guard Cutter Haddock later joined the effort, taking over search-and-rescue operations that afternoon, Valor said. The San Diego Lifeguard Service also assisted.

Search operations ended at approximately 6:20 p.m.

In all, Coast Guard crews logged more than 11 combined hours searching waters near Torrey Pines State Natural Reserve and La Jolla Shores. The search spanned from roughly 6 a.m. to 6:20 p.m., covering a stretch of coastline familiar to surfers, kayakers and beachgoers.

"After exhausting all reasonable search efforts, we have made the difficult decision to suspend active search operations," Cmdr. Celina Ladyga, acting commanding officer of Coast Guard Sector San Diego, said in a statement. "Our thoughts remain with the missing individual's family and loved ones."

Authorities have not disclosed what Youngs said in her last contact with family, Fox 5 San Diego reported.

Youngs is described as 5 feet 3 inches tall, approximately 115 pounds, with brown hair and hazel eyes. No clothing description was available in the alert.

Anyone with information is asked to call the Coast Guard Joint Harbor Operations Center at 619-278-7057 or the San Diego Police Department at 619-531-2000.