Experts Andrew Russell and Colin Andrews said the Wiltshire County, England, police sergeant, who was not named, told them he saw three figures standing around a fresh crop circle in a field near Silbury Hill in the county and stopped to investigate, The Daily Telegraph reported Wednesday.
"At first, he thought they were forensic officers as they were dressed in white coveralls. He stopped his car and approached the field," Russell said. "The figures were all over 6 feet and had blond hair. They seemed to be inspecting the crop. When he got to the edge of the field, he heard what he believed to be a sound not dissimilar to static electricity."
Russell said the trio fled the off-duty officer "faster than any man he had ever seen."
Andrews said he is "quite convinced the officer had an experience that day and one that we have not fully explored."
A Wiltshire Police spokesman said the department has no comment on the matter.
"The police officer was apparently off duty when this happened so we have no comment to make because it is a personal, not a police, matter," the spokesman said.