A 19-year-old Alexandria woman was killed and eight others were injured early yesterday when their 23-foot cruiser slammed into an 80-foot barge in Mattawoman Creek in Charles County, a spokesman for the Natural Resources Police said last night.

Stephanie Anne Nobilio was dead at the scene, said the spokesman, Cpl. Ralph Parker. He said Nobilio and eight other people in the Wellcraft cruiser were thrown from the boat about 4:40 a.m. after striking the barge anchored in the creek, a tributary of the Potomac River just north of Route 228 near the northern boundary of Charles County.

Parker said the other boaters were taken to Physicians Memorial Hospital in Charles County and Prince George's Hospital Center, and that two of the eight were in critical condition last night.

The boaters taken to the hospitals were: Michael Heine, 36, of Lorton, who officials believe was the operator of the boat; Christopher Davis, 23, of Ft. Meyer; Stephen Allman, 23, of Alexandria; Derrick Abney, 34, of Washington; George Jenkins, 28, of Fairfax; Tom Fuller, 20, of Alexandria; Gina Drake, 25, of Woodbridge; and Tammy Bright, 23, of Alexandria.

Parker said investigators do not know what caused the accident. Further details were unavailable yesterday.