SANTA FE, New Mexico (Reuters) - New Mexico's worst wildfire, just contained after roaring through Los Alamos and the premier U.S. nuclear weapons lab two weeks ago, spread again briefly in a forested canyon, officials said on Friday.

Spot fires caused by wind-blown embers were put out but about 700 firefighters remained on guard because the forecast said there would be more windy storms, U.S. Forest Service spokesman Joe Pasinato.

High winds late on Thursday blew embers past a fireline to start the latest spot fires on about five acres (2.02 hectares) on the western edge of the blaze, which has consumed over 47,650 acres (19,280 hectares) since May 4.

The fire, started by National Park Service brush burning on May 4 that raged out of control, destroyed over 200 houses and apartment buildings in Los Alamos and scorched the grounds of Los Alamos National Laboratory, the birthplace of the atomic bomb.

Thursday's outbreak was on the fire's western edge in a steep, remote area of Guaje Canyon, about five miles (8 km)northwest of Los Alamos.

``There are a few small homes in the area but none of them are endangered,'' Pasinato said.

The blaze had been classed as fully contained on Wednesday. In wildfire terms, containment means the blaze is surrounded by firelines or already burnt areas and is not advancing.

With the latest outbreak and the threat of more wind-driven spot fires, officials pushed back the estimated date for full containment to May 29.

After that, the fire will most likely continue to smolder, smoke and flare up within its 89-mile (143 km) perimeter until New Mexico's summer rainy season starts in late June or July.