NEW YORK (Reuters) - A family vacation turned into tragedy when a mother drowned while trying to rescue her son and his friend in the choppy waters of Lake Erie in western New York, police said.

Christen Stefan, 37, swam into the lake in Westfield, New York, on Wednesday to save her 9-year old son, Tyler, and a friend who were riding an inner tube when the wind pushed them into deep waters, the Chautauqua County Sheriff's Office said in a statement.

The wind and current carried all three to a cove with a rocky cliff at the shore line, which they attempted to climb, the statement said.

The 8-year-old friend was able to climb to safety but Tyler fell back into the water. Stefan plunged in after him, but disappeared under the waves.

Tyler was pushed some 200 feet (61 meters) farther offshore before a local resident was able to rescue him. He was treated for hypothermia.

Stefan, who lived Bethel Park, Pennsylvania, near Pittsburgh, was pulled from the lake but pronounced dead at a nearby hospital.

(Reporting by Curtis Skinner; Editing by Ellen Wulfhorst, Bill Trott and Gunna Dickson)