( CNN ) -- Federal investigators , joined by local officials and others , spread across Alaska on Thursday seeking the cause of a plane crash that killed five people , including former U.S. Sen. Ted Stevens . Deborah Hersman , the chairman of the National Transportation Safety Board , told reporters that the initial investigation of the crashed airplane was complete . The wreckage would be hauled to nearby Dillingham , Alaska , to be examined further , Hersman said . There was no new information on what caused the plane to crash Monday on a rugged mountainside in southwestern Alaska , killing Stevens and four others . Another four passengers survived , including former NASA head Sean O'Keefe . Stevens , who served in the U.S. Senate for 40 years , was 86 . His funeral will be held next Wednesday at 2 p.m. ( 6 p.m . ET ) at the Anchorage Baptist Temple in Anchorage , according to Jim Manley , a spokesman for Senate Majority Leader Harry Reid . O'Keefe remained in critical condition on Thursday , according to Kirsten Schultz , a spokeswoman for Providence Alaska Medical Center . The condition of O'Keefe 's son , Kevin , was upgraded to fair from serious . Another survivor , lobbyist Jim Morhard of Alexandria , Virginia , was also upgraded to fair from serious . Thirteen year-old William Phillips , whose father died in the crash , remained in good condition , Schultz said . A CNN reporter who flew over the crash site Thursday said there was a wide , brown swath cut through the trees by the plane . The crash occurred about 1,000 feet up the 2,300-foot mountain in an area called Muklung Hills , about a 20-minute flight from Dillingham , the reporter said . Hersman said the de Havilland DHC-3 Otter involved in the crash was manufactured in 1957 and overhauled in 2005 from a piston to a turbine engine . She also confirmed the plane lacked either a Ground Proximity Warning System or an Enhanced Ground Proximity Warning System . The devices , which Hersman said are not required , help pilots determine how far they are above ground or terrain and can predict whether a plane is on a path toward an obstacle or mountains . Hersman said it was too soon to know whether any technological factor contributed to the crash . John Bouker , the commercial pilot who first spotted the crash site , told CNN Thursday that Stevens ' plane `` was messed up but not beyond survivability . '' `` It looked survivable , '' Bouker said , `` but it did n't look like it would be a very fun ride or anything . The wings were bent back . The nose section was messed up . It did n't look like a good situation to be in , that 's for sure . '' The aircraft , which was taking the group on a fishing trip , crashed in an area near the Bering Sea noted for its rugged terrain . Tom Tucker , a helicopter pilot who landed at the crash site , told CNN that when he first arrived , the survivors `` were coming in and out of consciousness . We put blankets over them to keep them warm . '' The longest-serving Republican senator in U.S. history , Stevens lost his 2008 re-election bid to then-Anchorage Mayor Mark Begich after being convicted on charges of making false statements on financial disclosure forms . A federal judge later dismissed the conviction , citing prosecutorial misconduct . Stevens survived a plane crash that killed his wife in 1978 ; he later remarried . CNN 's Patrick Oppmann and Paul Vercammen contributed to this report .
NEW : This means the product will ship as received by the manufacturer, sealed, with all advertised components, and with the manufacturer warranty. Two survivors upgraded from fair to serious condition , while another remains critical . One witness tells CNN the plane was `` messed up , '' but the crash was survivable . Stevens ' funeral will be held next Wednesday in Anchorage , Alaska .