A 64-year-old Prince George's County woman died yesterday after an electrical extension cord caught fire under her bed, burning most of her body, officials said.

Her seven grandchildren, ranging in age from 3 to 12, were safely evacuated from the house.

Mazie Hutcherson, of the 4300 block of Townsley Avenue in Hillcrest Heights, was in bed when the fire began just after 1 p.m., said Capt. Chauncey Bowers, a spokesman for the Prince George's County fire department.

Alerted to the blaze by a smoke detector, Hutcherson's son and two women who were in the house called 911, evacuated the children and tried in vain to reach Hutcherson, Bowers said.

Firefighters were able to get into her room, douse the flames and carry her out, Bowers said, but not before she suffered critical burns over 90 percent of her body.

"Unfortunately, she was right on top of this thing when it started," Bowers said. "This is just . . . a tragic situation."

Hutcherson was flown by helicopter to Washington Hospital Center, where a spokesman said she died shortly before 7 p.m.

The one-story brick house was owned by Hutcherson, whose husband died about 13 months ago, a neighbor said. Hutcherson had been ill and increasingly less independent over the past year or two, the neighbor said.

She lived with her son, his seven children and his fiancee. The children's mother was also at the house yesterday, visiting, the fiancee said in a brief phone interview.

Bowers said the extension cord under Hutcherson's bed was used to plug in a variety of appliances. The reason it malfunctioned was not immediately clear.

The resulting blaze, which caused $8,000 in damage, did not extend much beyond the bedroom and was extinguished quickly, Bowers said.