The search for 20-year-old Allyson Watterson was called off Saturday, six days after her boyfriend claimed they became separated while hiking

The search for an Oregon woman who allegedly disappeared while on a hike with her boyfriend has been suspended.

The search for 20-year-old Allyson Watterson was called off on Saturday — six days after her boyfriend, 21-year-old Benjamin Garland, claimed they became separated while hiking near North Plains.

Get push notifications with news, features and more.

“The active search is suspended, but the investigation is still going on,” Washington County Sheriff’s Office Deputy Brian van Kleef tells PEOPLE. “We exhausted all of our leads and clues in searching and it didn’t lead to the results we were looking for.”

“We haven’t given up,” he adds.

At a press conference Saturday, Watterson’s mother Misty said she will continue the search for her daughter.

“Even though they’re not actively searching, we will always search for Allyson,” she said, KOIN reports. “I will never stop looking for you—never, I’ll never stop. And I’d like to ask everybody else to not stop looking either.”

Watterson was last seen with Garland by a homeowner who spotted the couple around noon on Dec. 22 in the area — the day before she disappeared.

“We know they were in the area,” van Kleef says. “Where they were going and what they were doing is what we are still trying to figure out.”

However, police suspect they were not in the area to hike.

“We never really found evidence that was really going on,” van Kleef says. “There are no real trails out there to go walking on and that is why the whole hiking story doesn’t seem correct. What they were actually doing is still a mystery at this point.”

Garland was found on Dec. 23, asleep in another homeowner’s truck.

“The neighbor whose truck he was found sleeping in gave him a ride back to where he lived,” van Kleef says.

Want to keep up with the latest crime coverage? Sign up for PEOPLE’s free True Crime newsletter for breaking crime news, ongoing trial coverage and details of intriguing unsolved cases.

Garland and his father then went out looking for Watterson and when they couldn’t find her, Garland’s father reported her missing, around 30 hours after she disappeared.

“There is a 30-hour gap that is unaccounted for,” van Kleef says. “It is possible she was able to find her way somewhere else, but she is yet to turn up. We can try to guess what happened, but at the end of the day we don’t know. That is the hardest part for the family, not knowing.”

Police say they did find a stolen truck near where Garland was found.

“There is a stolen truck that we found near where we located him Monday, but we don’t know if it is the vehicle they drove out there in or not,” he says. “It was off the road. We don’t know if she was in the truck.”

Garland was later arrested on unrelated charges of theft and fraudulent use of a credit card. He was also charged in connection with the stolen vehicle that police recovered near where he was found.

Van Kleef says investigators are trying to track down the former owner of Watterson’s cellphone, which she used for WiFi only, in the hopes it might help aid in the search.

“It is an iPhone so if we can make it active and reactivate the old number, there is a chance it can still register and ping from a cell tower,” he says. “It is a shot in the dark, and we will give it a shot.”

Search and rescue crews had been looking for Watterson since the morning of Christmas Eve.