Safety officials say it could take months to figure out what caused a Lancair plane to crash near Sisters. The crash killed the two men in the plane. The two victims have been identified as Patrick Franzen, 52, of Bend, and the plane's owner and builder, Harry League, 68, of Chicago.   The crash was reported around 10:30 Monday morning by several eyewitnesses. The wreckage was found in a wooded area south of Sisters. At one point as many as 60 local volunteers were called in to look for the crash site. Forest Service Road 4606 will be closed today as the investigation continues and authorities are asking the public to avoid the area.