The disclosure came as Secret Service Director Mark Sullivan said "the Secret Service is deeply concerned and embarrassed" by his agency's "failing" in allowing the Michaele and Tareq Salahi access to the event. Among other duties, the Secret Service is charged with protecting the president.
The photo released by the White House this evening showed President Obama shaking Michaele Salahi's hand with Tareq Salahi looking on.
"The couple who attended the event without an invitation did meet the president in the receiving line," a White House official said.
The guest of honor, Indian Prime Minister Manmohan Singh, can be seen in the background, apprarently on the same receiving line. It is standard protocol at a state dinner for the president to introduce guests in the receiving line to the visiting head of state.
Sullivan said his agency's probe into the matter continues.
"The preliminary findings of our internal investigation have determined established protocols were not followed at an initial checkpoint, [specifically, the failure to verify] that two individuals were on the guest list," he said. "As our investigation continues, appropriate measures have been taken to ensure this is not repeated."
Despite the incident, White House spokesman Nick Shapiro suggested the president has confidence that the Secret Service is protecting him effectively.
"The men and women of the Secret Service put their lives on the line every day to protect us," Shapiro said. "They are heroes and they have the full confidence of the president of United States.
"The White House asked the United States Secret Service to do a full review and they are doing that," Shapiro added. "The United States Secret Service said they made a mistake and they are taking action to identify exactly what happened and they will take the appropriate measures pending the results of their investigation."
Salahis 'Love to Be in the Limelight'
Friends of the Salahis said the couple loves attention and said that they were invited to the White House gala event in honor of India.
"They love to be in the limelight," Casey Margenau said of Michaele and Tareq Salahi in an interview with "Good Morning America" today. "They love to be at a party, they like to be in front of everything and it would not have surprised me for them to have been invited."
Margenau threw the party at which the couple met and he was part of their wedding party. He said it didn't make much of a difference whether they were invited.
"They're in the limelight all the time … this is part of what they do, they enjoy it," he said. "And why not? Look how many people are talking about them right now. If you look on their Facebook page, most of it's positive … ."
Asked about speculation that the couple were in financial trouble, and sneaked into the dinner in a bid for a reality show they needed to shore up their finances, Margenau said he didn't have "any idea" where they were financially.
At one point, he said, he had contemplated purchasing a winery owned by the couple. The winery had been in trouble and the numbers didn't appear to be feasible, he said.
Friend: Salahis Will 'Land On Their Feet'
"I think that whatever they do, they'll land on their feet … They're a lot of fun, they know how to work a party and promotion, and parties are part of their lives," he said.
Another friend, Paul Wharton, said he has talked to the Salahis and that they were "in good spirits and pretty excited about all the attention but they really just wanted to get to the truth and let the story get out.
"They are very social people, they're a lot of fun," added Wharton, who said he met the couple years ago.
The couple spends a lot of time in India, so, Wharton said, he wasn't surprised that they would have attended the event.
The socialites were aspiring to appear in the upcoming reality-TV series "Real Housewives of D.C." and were being filmed by the show's producers when they sneaked into the White House for Tuesday's state dinner, ABC News has learned.
The Salahis weren't on the White House guest list, but that didn't stop the the duo from successfully penetrating one of the nation's most secure places.
Now, the Secret Service is investigating how the Salahis managed to pull it off and whether they committed a crime. It's unclear what legal liability, if any, they may face. Were they trespassing? Did someone at the White House help them get in?
"It's clear they weren't on the list and weren't invited," White House officials said.
Initial findings of the Secret Service investigation have identified a checkpoint where procedures were not properly followed, according to the agency.
For their part, the Salahis certainly looked as though they belonged, arriving in a stretch-SUV and wearing glitzy formal evening wear.
The couple posed for pictures on the red carpet with Vice President Joe Biden, White House Chief of Staff Rahm Emanuel -- whom Michaele Salahi called "Ron" -- and even slid up to ABC News' Robin Roberts for a snapshot.
"Once I entered the tent, somebody came up to me and I remember that she was dressed in, it seemed like authentic Indian attire," Roberts said. "When she walked away, I thought, again because of her attire, I thought that she very much fit in. There was never a time when I thought, 'Boy, what are they doing here?'"
The couple later posted pictures from the evening on their Facebook pages.
An ABC News camera outside the White House captured footage of the Salahis arriving. They were trailed by what appeared to be a TV crew.
A spokeswoman for the Bravo television network, which produces "Real Housewives," told ABC News, "Michaele Salahi is under consideration as a cast member and, as such, Half Yard Productions [the producers of the series for Bravo] were filming the Salahis on that day. That was the extent of our involvement."
Bravo added the couple told the crew they had been invited to the state dinner, which the producers had no reason to believe was untrue.
Obama Was Never in Danger
Secret Service spokesman Ed Donovan said the two were not escorted off the premises Tuesday night, but it's unclear whether they ever made it to a seat for dinner.
"It is a real concern if they would have had a different intent," Brad Garrett, a former FBI agent, said. "Could they have possibly physically attacked somebody? Of course they could have. They would have been wrestled to the ground and taken away. But it is a real concern about people's ability to penetrate security and then be next to people that it would be a huge issue if something happened to them."
Donovan said even if the two were uninvited guests, President Obama and other dignitaries would not have been in danger.
"Everyone that goes into the White House grounds goes through magnetometers and other levels of screening," he said.
ABC News' Steven Portnoy contributed to this report.