An aerial survey of 260 miles of natural-gas pipeline in Washington state showed the line is safe to return to service except for 15 questionable miles south of Yelm, Northwest Pipeline Corp. said Friday.

Crews were working to get the rest of the line fully functional by the weekend, company spokeswoman Susan Flaim said in a telephone interview from Salt Lake City.

The 26-inch-diameter pipeline that runs from Sumas, at the Canadian border, south to Washougal at the border with Oregon, had been shut down for inspection after it sustained two explosive ruptures last weekend.

On Thursday, geotechnical consultants and other experts began surveying the line by helicopter, looking for any spots where land had slipped around it. Such slippage, probably caused by recent heavy rains, is the suspected cause of the two explosions and fires last weekend - one near Everson near the Canadian border and the other 200 miles south, near Kalama along the Columbia River. No one was injured in either explosion.

The survey, completed Friday, showed “suspicious land movement activity” in the Yelm area, about 50 miles south of Seattle, Flaim said.