The reported disappearance of Karissa Boudreau, 12, sparked a two-week search in Bridgewater, a community of 8,000. (Canadian Press)

The mother of Karissa Boudreau, a 12-year-old girl whose body was found near Bridgewater, N.S., last February, has been charged with first-degree murder in her daughter's death, police said Saturday.

Police arrested Penny Boudreau, 34, in Halifax on Friday.

At a news conference by the RCMP and Bridgewater police on Saturday, investigators provided a brief statement and would say only that they do not expect to lay any other charges.

"Investigators feel confident that there was only one person responsible for this homicide," said Bridgewater Chief Brent Crowhurst.

"Karissa must've known her killer," RCMP Supt. Blair McKnight said.

He thanked citizens for their help, saying "a number of them provided valuable information."

Karissa was reported missing Jan. 27 from the parking lot of a grocery store in the town as a snowstorm descended on the region. Penny Boudreau told police she had argued with her daughter that day as they drove to the store.

Boudreau said she went into the store, leaving the girl in a car. When she returned, she told investigators, Karissa was gone.

Two days after she reported her daughter missing, Boudreau appealed to the public for help at an emotional news conference.

The girl's body was discovered Feb. 9 by a passerby on the banks of the LaHave River, just south of the town.

Penny Boudreau was to appear in court in Bridgewater on Monday morning, with extra security.