That same staff writer, on Sunday, June 20, 2004, wrote:
Quote:
Federal prosecutors are preparing to seek criminal charges against former Enron Corp. chairman Kenneth L. Lay, capping a 2 1/2-year-old investigation into the collapse of the Houston energy company, said sources involved the probe.
So I think that is a major typo with a "6" and a "7" added in, possibly because of some sort of printing quality control count. Remove the "6" and "7" and then the phrase reads "2 1/2"-year-old investigation.