PHOTOS: Celebrity mug shots
Under a conservatorship, which must be granted by a judge, a person turns over the most basic decisions of their life to another person or persons, including about money, medical treatment and even where they live.
Bynes' parents have expressed concerns about her welfare for more than a year and discussed seeking a conservatorship, according to a source familiar with the actress but not authorized to discuss the matter publicly.
They visited her Wednesday.
Britney Spears' parents obtained a conservatorship after a series of erratic incidents in 2008, including a much-publicized visit to a salon where she had her head shaved. In Spears' case, her father has overseen her life with a court-ordered attorney since she was deemed legally incompetent.
Bynes was detained Monday by Ventura County sheriff's deputies and is being held for an involuntary mental-health evaluation, authorities said.
Bynes was detained after igniting her pant leg while setting a small fire with a gas can in the driveway of a Thousand Oaks home, according to deputies and witnesses. The actress grew up in Thousand Oaks, where her father had a dental practice.
Bynes, already facing drug charges in New York and the subject of a series of charges in L.A. County, was taken into custody for her own safety under California's Welfare and Institutions Code, known as a 5150 hold, after the incident, Sheriff's Capt. Don Aguilar said.
Under the law, she can be held for 72 hours. But sources familiar with the incident say the actress may be held another 14 days if she is determined to be a danger to herself or others.
A witness who called 911 reported seeing Bynes with a small gas can and was concerned it could explode.
Andrew Liverpool told reporters he saw "this girl lying down here with her left pant leg on fire and there is this gas can right here and it is trailing fire."
Liverpool said that when he went to help she had already managed to snuff out the flames on her pant leg.
He said Bynes was with a small dog and that when he asked if she was OK, she said she was fine.
As he was moving the gas can away and others arrived to help, he said, Bynes left the scene, but he found her on the next block. He said she then tried to leave in a cab, but he told the driver not to take her anywhere.
When he looked at her he said he realized "it is Amanda Bynes." He said Bynes claimed that her dog had been burned.
Deputies arrived at the home in the 200 block of Avenida de los Arboles about 8:46 p.m.
"There was a call about a small fire that she'd apparently set in front of the residence, kind of out on a sidewalk on the concrete," Sgt. Eric Buschow said. "It wasn't an attempt to burn down the house or anything."
Buschow said the fire caused no property damage.
Police investigate overcrowded Hancock Park home
Police investigate fatal shooting of man in Baldwin Park
Democratic leaders ask Filner to resign amid sexual harassment claims
Twitter: @lacrimes| Google+