(FOX40.COM) -- The Butte County Sheriff's Office said the use of divers and sonar technology has been "exhausted" in the search for brothers Andruw and Wesley Cornett who went missing at Thermalito Afterbay earlier this month.

The sheriff's office said it will focus on more limited surface search methods including "aircrafts, drones, boats, on-shore vehicles, and K9s."

Rescue and recovery crews have been searching for the pair since Wesley Cornett, 17, went into the water when his kayak overturned while duck hunting on Dec. 14. Andruw Cornett, 19, went into the water to help his brother. Neither brother has been seen since.

A wallet belonging to one of the brothers was discovered during the search last week.

Authorities have cited the thick vegetation and low visibility in the lake as hindrances to the search.