By Keith Coffman

DENVER (Reuters) - Police on Friday arrested a 12-year-old Colorado girl accused of trying to kill her mother twice by poisoning her with bleach for taking away her iPhone, authorities said.

Boulder County Sheriff's Commander Heidi Prentup said in a statement that the mother drank the caustic fluid on one of the two attempts, which both happened within a week this month.

On March 2, the girl poured bleach into a breakfast smoothie that she had prepared for her mother, Prentup said.

"Mom noticed an odor of bleach in the drink and thought her daughter had cleaned the glass prior to making the beverage and did not rinse all the bleach out," the police statement said.

The woman, who was not named by the authorities, was treated at a local hospital and released.

Four days later, the girl allegedly poured bleach into a water carafe her mother kept in her bedroom. When the woman smelt bleach, she became suspicious and confronted her daughter.

"This is when she learned her daughter had developed the plan to kill her for taking away her iPhone," police said.

Prentup said the mother reported the girl to police, and that investigators then gathered enough evidence to take her into custody.

The girl was taken to a juvenile detention facility on Friday where is being held pending the filing of charges.

(Reporting by Keith Coffman; Editing by Daniel Wallis and Sandra Maler)