HILLSBORO, Ore. -

A woman and her boyfriend were arraigned Wednesday on charges they killed two girls who were playing in a pile of leaves in a Forest Grove street.

The 18-year-old woman, Cinthya Garcia-Cisneros, is charged with felony hit-and-run. Her 18-year-old boyfriend, Mario Echeverria, is charged with hindering prosecution.

Police say when they were driving Sunday night they intentionally ran over a mound of leaves and heard a bump.

The accident killed 6-year-old Anna Dieter-Eckerdt and her 11-year-old stepsister, Abigail Robinson.

Garcia-Cisneros said she was afraid to identify herself to police. Her boyfriend is accused of taking the car to a car wash to eliminate evidence.

The Oregonian reports the pair are due back in Washington County Circuit Court next Wednesday