The lost e-mails apparently were deleted from the computer of John A. Rogale, the DRPA's director of labor contract compliance, during an 18-month period in 2012 and 2013.
Rogale, who retired from the DRPA in April 2013, was known in South Jersey political circles as the former president of the Washington Township Council and an aide to John Matheussen during Matheussen's tenure as a Republican state senator.
Matheussen brought Rogale with him to the DRPA when he became chief executive of the agency in 2003. Matheussen resigned in January when Christie appointed him a Superior Court judge.
Officials at the DRPA said that Rogale was not involved with economic development spending at the DRPA, and that the loss of the e-mails was inadvertent, apparently caused by a software malfunction.
"The Delaware River Port Authority board was recently advised that there may be a compromise to a data storage effort that was implemented to assist with a federal investigation," the DRPA said in a statement.
"The DRPA has directed its special outside counsel to continue to be open and transparent in providing assistance to the federal investigation and to assist in the effort to determine if a compromise has occurred."
The outside lawyer and federal investigators are to meet this week to determine how to proceed. Options range from an effort by the DRPA to try to recover the e-mails to a seizure of DRPA computer hardware by federal investigators.
DRPA board members were alerted to the erased e-mails in a closed-door meeting last Thursday with top DRPA officials and the outside lawyer hired to deal with the federal probe.
One of the board members, Philadelphia labor leader John "Johnny Doc" Dougherty, said Wednesday, "If it's true, it's a flat-out obstruction of justice, and it has to be handled immediately."
"The whole DRPA is at stake. . . . I have a lot of questions for DRPA leadership, past and present."
Dougherty, who represents Pennsylvania Auditor General Eugene DePasquale on the board, has been a frequent critic of DRPA management.
DePasquale, who was not in the closed-door meeting, said Wednesday the disappearance of the e-mails "is very concerning."
"The DRPA needs to do exactly what the federal investigators tell us to do . . . and if it turns out that anyone acted inappropriately or illegally, they should be punished to the fullest extent of the law," he said.
DePasquale said "there is a significant amount of public trust that has to be regained by the DRPA."
Jeffrey L. Nash, the Camden County freeholder who is vice chairman of the DRPA board and leader of the New Jersey delegation on the board, declined Wednesday to comment on the lost e-mails.
A spokeswoman for the U.S. Attorney's Office in Philadelphia, Patricia Hartman, also declined Wednesday to comment, saying only that "we can't confirm or deny investigations."
Rogale said Wednesday that he routinely deleted his e-mails to prevent them from accumulating, but he said he did not know how to erase them from the computer system.
"I deleted them every day. It's not unusual for people to delete e-mails," he said. "But to erase them for all time? I don't know how to do that. On a scale of 1 to 10, when it comes to computers, I'm a zero."
He said he had no involvement with economic-development at the DRPA, and expressed surprise that his e-mails would interest investigators.
Rogale retired on April 30, 2013, a month after the U.S. Attorney's Office issued a wide-ranging subpoena for all records dealing with economic-development spending by the DRPA.
In response to that subpoena, DRPA general counsel Danielle McNichol and inspector general Thomas Raftery instructed DRPA employees to preserve documents, records, and e-mails.
Even e-mails that had been deleted by employees could be preserved by computer software, but a software malfunction apparently allowed Rogale's e-mails to be erased permanently, according to the DRPA's account.
The 15-month-old federal investigation is focused on spending by the DRPA on economic development projects.
The DRPA spent nearly $500 million over 15 years to underwrite museums, stadiums, a concert hall, a cancer center, the Army-Navy football game, and other non-transportation projects.
Much of the money went to politically influential recipients, as the Pennsylvania and New Jersey delegations on the DRPA board got equal amounts to spend.
The DRPA board voted in 2010 and 2011 to end economic development spending, after nearly all the money borrowed for that purpose had been spent.
Several economic-development projects remain on the DRPA's books, totaling $22.7 million, DRPA chief executive John Hanson said Tuesday in testimony to the Pennsylvania Senate transportation committee.
Of that, about $5.2 million remains for Pennsylvania projects and $17.5 million for New Jersey projects.
Hanson said the DRPA was obligated to fund those projects under contracts approved before the self-imposed ban on economic-development spending.