The family of a 60-year-old California woman who went missing on a camping trip last week fear she has been abducted.

But they accuse the police of refusing to take seriously their concerns for Sheryl Powell, who was reported missing around 2pm on Friday.

Sheryl disappeared near a campsite in Inyo County after getting out of her car with the family dog, Miley, for no more than five minutes while her husband Joseph Powell parked their car further up a slope, according to son Greg Powell.

Sheryl Powell, 60, went missing in California's Inyo County on Friday. The missing poster (right) posted online by her son Greg, stresses his belief that she was abducted

The missing woman with her husband, Joseph. Their son Greg has dismissed suspicions Joseph had anything to

Joseph searched for his wife for an hour around the spot about a mile west of the Grandview Campground in the White Mountains, walking circles, blowing a whistle and yelling, before raising the alarm via a satellite device he was carrying.

In a Facebook post on Saturday, Greg complained that the Inyo County Seriff's Office had only mobilised 'a small pool of people,' eight on Friday and 17 on Saturday, to search for his mother 'with mediocre results.'

And police were 'refusing to acknowledge' the 'high likelihood of abduction' in Greg's view.

'They keep insisting she just got lost (she didn't bring any food or water and had no plans to hike yet, they were just setting up camp) or the dog got away (she weighs 4 lbs was on a leash and has a bad leg so she can't run),' he wrote.

'I hope they're right but I think they should be pursuing the possibility of abduction as well.'

Greg dismissed officials' suspicions that his father had anything to do with his mother's disappearance.

A helicopter equipped with thermal imaging gear has been taking part in the search for missing Sheryl Powell

'So far the criminal side of the investigation has focused on my dad and on my mom's friends as suspects, both of which ideas are absurd,' he wrote.

'My parents have an extremely loving relationship and my dad (who has refused to leave the campsite) is on the verge of breakdown.'

The sheriff's office said it began a search of the area as soon as it received the alert on Friday, including a helicopter fitted with thermal imaging equipment.

But Greg said at the weekend the helicopter search would be called off in two days if Sheryll is not found, and has started a GoFundMe crowdfunding campaign to continue chartering the helicopter beyond that time.

Meanwhile Greg and his sister are distributing missing posters of their mother in the area.

The Inyo County Sheriff's Office said it was conducting a search and rescue operation along with a criminal investigation

'In addition to this being an active search and rescue, it is also an active investigation,' the sheriff's office said.

'If anyone has any information that can assist in locating missing camper, Sheryl Powell, please call the Inyo County Sheriff's Office at 760-878-0383, option 4.'

Sheryl, described as an experienced hiker, is 5-feet 3-inches tall, 120 pounds, with brown hair and brown eyes, and she may be wearing a purple top.

Miley, a black-and-white Yorkipoo, or Yorkshire terrier-toy poodle cross, has a red leash.