A series of emails from State Department officials on the ground in Benghazi, Libya, suggest that officials in the White House and intelligence community knew within hours of the September attack on the U.S. Consulate there that the militant group Ansar al Sharia had claimed responsibility for the violence.

According to the emails, first reported by Reuters, between 300 and 400 national security officials were receiving real-time updates as the raid was playing out. One of those emails came just after 6 p.m. Eastern Time, with the subject heading "Update 2: Ansar al-Sharia Claims Responsibility for Benghazi Attack (SBU).”

SBU is shorthand for "sensitive but unclassified."

The email exchanges are likely to put new pressure on the Obama administration to explain why, five days after the attack, U.S. Ambassador to the United Nations Susan Rice argued the violence — which left four Americans, including U.S. Ambassador to Libya Christopher Stevens, dead — was a "spontaneous" reaction to an anti-Islam video posted on YouTube. 

Top Republicans, including presidential nominee Mitt Romney, have argued that the administration held off acknowledging that the violence was a terrorist attack for political reasons.

The White House has maintained that from the beginning, it had been clear that an investigation was ongoing and that new information about what happened would be turned over as it became available.

And while the emails do suggest that the intelligence community knew early on that the attacks might have been an act of terrorism, they also speak to the confusion on the ground. One email, which arrived just after 4 p.m., indicates that Stevens had been moved to a "compound safe haven." Americans later learned he had been killed in the attack.

On Tuesday, Vice President Biden, during an interview with CBS, said that Rice and President Obama shared "exactly what … the intelligence community was giving us and briefing us on" in the days following the attacks.

House Oversight Committee Chairman Darrell Issa (R-Calif.) has launched a probe into the attack, with Republicans questioning whether the administration had denied requests from diplomats for heightened security measures in Libya.