HAPPY VALLEY-GOOSE BAY, N.L. - The mother of a boy who went missing last month and died on the sea ice off Labrador has written a letter to Prime Minister Stephen Harper calling for an investigation.

Elizabeth Rice says she wants to know more about how the Canadian military handled a calls to help during the search for her son, 14-year-old Burton Winters.

Rice calls the Defence Department's response "ineffective."

She is also raising questions about the department's reasons for not immediately launching a helicopter search when the first of two calls for help were made.

Earlier this month, the Canadian military said nothing it could have done would have saved the boy's life.

A military investigation concluded no military chopper was available to fly from Happy Valley-Goose Bay when the first request came Jan. 30 to search for Winters, whose body was found two days later.