Sinn Fein leader Gerry Adams was refused entrance to the White House Irish community St. Patrick’s reception last night in a shock occurrence that left Irish American leaders baffled.

Leading congressional figures promised an immediate inquiry. Richie Tranghese, key Irish staffer for Congressman Ritchie Neal, said the refusal would be immediately addressed.

Adams arrived with other Sinn Fein personnel including the party's Vice President Mary Lou McDonald.

Adams was pulled aside from the other Sinn Fein members as the White House security personnel examined his documents.

Adams is known to face what is called “secondary inspection” when boarding planes for North America and he usually arrives very early for flights, but problems at the White House level are highly unusual.

That is because anyone attending the event is known to have been screened by the FBI and Secret Service before being issued with the official invite.

Today, Adams posted a photo of his invite and the confirmation of his RSVP to Twitter:

My invite 2

The White House. Just saying. pic.twitter.com/0fGax1LMhB — Gerry Adams (@GerryAdamsSF) March 16, 2016

Confirmation of my invite 2 White House Reception. From the White House. pic.twitter.com/lMTVXp05MP — Gerry Adams (@GerryAdamsSF) March 16, 2016

Why he was denied entry is still unclear. Even in cases where, for instance, an Irish passport holder may have his passport in Irish, as happened to a TD recently, usually a way around the issue is found.

However, after waiting 90 minutes and seeing no movement in the effort to gain him entrance, Adams decided to leave.

The departure of Adams, a prime architect of the IRA ceasefire and the peace process, is an embarrassment for the Obama administration, who will struggle to explain how Ireland's third most popular party leader in the Irish Republic and a huge vote getter was left standing outside.

Present at the White House was Deputy First Minister Martin McGuinness as well as a slew of members of the House and Senate.

In his remarks President Obama lamented he was holding his last St. Patrick’s Day party and referred to Irish immigrants on Famine ships and blacks on slave ships and stated he was delighted that his daughters would have different ethnic backgrounds to explore.

For his part, Enda Kenny thanked Obama for his help and support for Ireland over the past seven years and stated there would always be a place in Ireland’s heart for him.

Earlier, at a breakfast hosted by Vice President Joe Biden, Kenny referred to the recent tragic loss of the president’s son Beau from cancer and stated the people of Ireland stood with him in his time of agony.

At the speaker’s lunch Speaker Paul Ryan stated he had recently visited his roots in Kilkenny and they were not that distant from Obama's in Moneygall. He explained that the Speaker’s Saint Patrick's Day lunch had been started to help facilitate dialogue between the parties and he hoped that would be the case.