Japanese police trudged through waist-high mud on Thursday in another unsuccessful day searching for a missing Auburn University student, though his parents said they remain optimistic about their son’s potential rescue.

Subscribe to read this story ad-free

Get unlimited access to ad-free articles and exclusive content.

Thursday’s efforts by “incredibly thorough” rescuers to find James “Weston” Higginbotham, 20, were conducted in “difficult conditions,” mother Nancy Higginbotham said in a statement late Thursday.

“It’s been a long, stressful day,” she posted. “Today, dozens of Japanese police officers searched through waist-high mud in an effort to find Weston. Search dogs and helicopters were also deployed.”

Higginbotham was last seen Friday at the Kyoto train station, launching a massive search by police and local volunteers, the family has said.

Higginbotham’s loved one said they still have great “confidence in the professionalism and dedication of the Japanese authorities and do not believe any area within the search zone was overlooked.”

“They are meticulous,” the mother added. “The area where we believe Weston is missing has ample water and limited berries. There is still hope.”