SEAT PLEASANT, Md. (AP) _ Fire swept through a frame house on Thanksgiving Day, killing six children who were trapped in the upstairs bedrooms and injuring six adults, authorities said.

''All I saw was fire coming out of every window,'' said Gloria Roberts, a neighbor. ''People were screaming, jumping out of windows. I couldn't believe what I saw. It was awful.''

Neighbors said the house - a white, two-story bungalow in a modest area near Washington - was inhabited by James Williams, 57; his wife, Annie, 47; a son, Joshua, 10; two daughters, Sandra, 23, and Tracy, 25, and their seven children.

Those who died were identified by Prince George's County fire officials as Joshua; Tracy's three children, Clifton Ahmad Jr., 5, Justin Ahmad, 3, and Sheena Ahmad, 1; and Sandra's twin 9-month-old boys, Nathaniel Mark Williams and Emmanuel Matthew Williams. Two of Sandra's children - Samuel A.J. Williams, 3, and James Q.R. Williams, 4 - were sleeping in a downstairs bedroom and got out of the house.

Ward Caddington, the deputy fire chief for Prince George's County, said 14 people were in the house when fire broke out, apparently on the first floor. Besides the Williams' family, there were two visitors, neighbors said.

The cause of the fire has not been determined, but Caddington said flames spread quickly in the older, frame building with a front porch.

Fire officials were told there was a smoke detector in the house, but they did not know whether it functioned, he said. They were also examining a kerosene heater found in the house.

Wayne McBride, a police officer on a routine patrol, spotted smoke pouring from the house about 8 a.m. ''I called the fire department and went to the back steps to find somebody, but it (the fire) was too bad and pushed me back,'' said McBride.

''The adults had already made it out. They were lying all around the house where they had jumped from the roof or windows,'' he said.

When firefighters arrived a few minutes later, Caddington said there was ''no chance of rescue'' because of flames and smoke. They extinguished the blaze.

The children, clad in their pajamas, were found in two bedrooms on the second floor of the house. There were all ''in or near the beds,'' he said.

Authorities would conduct tests on the autopsies to determine what caused the deaths, he said.

Six adults, including one firefighter, were taken to Prince George's Hospital Center with minor injuries. Nursing supervisor Karen Frank said they were being treated for smoke inhalation and lacerations. She would not give the names of the injured.

After the fire, friends and neighbors, almost all of whom knew the Williams' family, huddled in small groups on the quiet street under sunny skies that pushed the temperatures into the 70s.

The house, its charred inside visible, was roped off by fire and rescue teams. Caddington said the fire was the worst in the country in a decade.

''They were a close-knit, friendly family,'' said Joan Perry, who went to the same church as the Williams' family. She said Annie and James Williams had both experienced some health problems which prevented them working.