A judgment against the United States cannot be sustained upon a theory of absolute liability. Dalehite v. United States, 346 U.S. 15, 44-45, 73 S.Ct. 956. Since the court below made no express finding as to negligent conduct on the part of the United States it is necessary to vacate the judgment and remand to the end that appropriate findings may be made. We make it plain, however, that we do not pass upon the question whether the record would or would not sustain a finding of negligence against the United States. This is a matter which rests with the trial court.

The judgment appealed from will bb vacated and the case is remanded with the direction to proceed in accordance with this opinion.