The National Transportation Safety Board announced Friday that it had finished its work in Paulsboro, nearly exactly a week after the Nov. 30 derailment.
The NTSB says it will have a preliminary report completed in about two weeks.
Meanwhile, the site cleanup is continuing as crews remove derailed cars.
Officials have said they expect hundreds of evacuated residents to be able to return to their homes Sunday.
U.S. Sen. Robert Menendez is heading to the area on Friday for a briefing.
(Copyright 2012 by The Associated Press. All Rights Reserved.)