A woman was arrested last week in Fairfax County after a 10-year-old boy was reported alone on the rear deck of a house, knocking on the door and crying, the Fairfax County police said.

Police said Friday that it was alleged that the child’s mother had intentionally placed him outside the house, in the 7400 block of Roudsby Court, on Thursday night.

The police said Julia Brandt, 31, of Alexandria, was taken to the county’s adult detention center and charged with felony child neglect.

Custody of the 10-year-old, and of a second child found at the home, was arranged with a friend of the family, the police said.

John Torre, spokesman for the Fairfax County school system, said Brandt was a teacher at an elementary school there. She has been placed on leave, he said. Brandt could not be reached immediately on Sunday night.

This report has been updated.