DULUTH — Authorities are investigating a fatal boat crash on a northeastern Minnesota lake.

St. Louis County sheriff’s officials said four people were on a boat that struck a dock and boat lift on Dinham Lake in Ellsberg Township Saturday about 11 p.m.

Fifty-four-year-old Ann Marie Delanghe suffered life-threatening injuries and was thrown into the water upon impact. The Burnsville woman was rescued from the lake by witnesses on shore. She was taken to Essentia St. Mary’s Hospital in Duluth, where she was later pronounced dead.

Two others in the boat were taken to a Virginia hospital. The fourth person refused medical treatment.

The Sheriff’s Office said the driver of the boat is under investigation. Authorities said speed, alcohol and darkness are factors in the crash.