PLYMOUTH — Law enforcement officials in California are now calling the February disappearance of a former Maine woman a “suspicious missing person case,” officials from two agencies confirmed this week.

Danielle Bertolini, 23, was reported missing to Fortuna, California, police on Feb. 19. Her family last had contact with her on Jan. 29, according to her mother, Billie-Jo Dick of Plymouth.

Dick said at the time that this was unusual behavior for Bertolini, a former Nokomis High School student who usually maintained daily contact with her sister, Mariah Bertolini. In a followup interview late last month, Dick said she fears her daughter is dead.

“The last time that I talked to her was in January, on the 29th, and Danielle always knew that if I didn’t hear from her within a three-week span that I would be calling around, trying to locate her and calling her sister and whatever,” Dick said late last month.

“Mariah usually spoke to her a lot and would let me know that, ‘Yes, Mom, Danielle’s OK. She’ll call you when she gets somewhere where she can and that type of thing because Danielle, she would have a few different places where she used to stay. Not all of them good, but some of them good,” Dick said.

Mariah Bertolini, who lives in the Seattle area and is visiting Maine this summer, agreed.

“She just didn’t call me,” she said last month. “ The last time I talked to her she was supposed to call me back. She said, ‘I’m gonna go lay down. I have a stomachache’ and she was gonna call me back when she got up.

“Well, she didn’t call me back and so I kept calling the place that she’d been staying at for a while and nobody answered. And you know, I thought it was kind of weird. Like, even if she wasn’t there, [a man who lived there] would always answer the phone,” she said.

Dick flew to the West Coast in late February for a two-week search effort coordinated from Maine by Richard Bowie, operations director for the Down East Emergency Medical Institute, a volunteer search and rescue group to which Dick belongs.

Participating in the search were about 15 family members and friends from her home state of Oregon, who pounded the streets, distributed fliers, got the word out on missing person Internet sites and spoke to Danielle’s friends and acquaintances and others they thought might have knowledge about her daughter’s whereabouts.

Dick also said that police in California have told her they were providing information about the circumstance surrounding the case to the Humboldt County District Attorney’s Office.

Police initially told Dick they considered her daughter a “voluntary” missing person because of her age, and as such, their ability to assist was limited. Police now believe her daughter’s disappearance is suspicious.

That’s because Danielle went missing at roughly the same time as another area woman, 37-year-old Sheila Franks of Rio Dell and Loleta, California, who last was seen on Jan. 11, according to a missing person flier posted on the Internet by her sister, Melisa Walstrom of Alaska.

Both women have blond hair and blue eyes, are similar in appearance and build, and travel in the same social circle.

Family members of both women, who have joined forces in the search effort, say that police have told them that they believe the two missing persons cases are linked because Danielle Bertolini and Sheila Franks are believed to have last been seen with the same 43-year-old Fortuna man before they vanished.

“That person of interest has been cooperative with us,” Lt. Wayne Hanson of the Humboldt County Sheriff’s Department said this week. Humboldt County police are working with Fortuna police on the cases, he said.

“It’s an active investigation,” Hanson said, adding there are some “red flags” in the cases. He said that police have received numerous tips, have interviewed several people and searched several areas in an effort to find the missing women. Authorities also have submitted evidence to a crime lab and are conducting a forensic study of cellphones and are looking into cellphone tower activity, he said.

“It’s definitely suspicious, but there’s nothing to support any foul play at his point,” Fortuna police Officer Brian Taylor said.

Dick is frustrated that the authorities in California aren’t doing more to find her daughter and bring charges against the person she believes killed her.

Taylor said he understood Dick’s frustration. He pointed out, however, “In our line of work, we deal with evidence and facts.”

Mariah Bertolini said that the person of interest claims that he dropped Danielle off at her former boyfriend’s house in Fortuna.

“She would not have gone there because he was in jail and she doesn’t get along with his grandma so she would not go there. So I know he was lying about that,” she said. “Then [he] ended up coming back later that night and dropped off the rest of Danielle’s stuff at [a friend’s house Danielle was expected to be at] and said she forgot it and that she had asked him to drop it off.

“I know my sister better than that. She doesn’t go nowhere without her stuff,” she said of Danielle’s makeup bag, toothbrush and other necessities.

Walstrom said in a recent telephone interview that Franks, who is her younger sister, was living with the person of interest in a tent in his mother’s garage and that the last known contact with family was a text message to Franks’ teenage son.

Anyone with information about Bertolini’s whereabouts should contact Fortuna police at 707-725-7550. Anyone with information about Franks’ disappearance should contact the Humboldt County Sheriff’s Department at 707-445-7251.