In a second security lapse at the November 24 event, the person, who was not identified, traveled from a Washington hotel where the Indian delegation was staying and arrived at the dinner with the group, which was under the responsibility of the U.S. Department of State.
"This individual went through all required security measures along with the rest of the official delegation at the hotel, and boarded a bus/van with the delegation guests en route to the White House," the Secret Service said.
A Secret Service spokesman was not immediately available to comment on whether the individual had any contact with Indian Prime Minister Manmohan Singh or came close to the visiting leader.
The person was not on the White House guest list. The individual did not go through the receiving line, unlike a Virginia couple, Tareq and Michaele Salahi, whose previously reported unauthorized attendance at the dinner has prompted a review of procedures and criminal investigation.
Besides coming within feet of Singh, the Salahis shook hands with President Barack Obama.
The White House declined immediate comment beyond the Secret Service release.