As anti-America violence continues across the Middle East, many are wondering what warnings the United States may've had before the attack in Libya that left U.S. Ambassador Chris Stevens and three others dead.

The British newspaper The Independent claims the U.S. State Department had credible information of the attack at least 48 hours before it took place. But even with that warning, there was no instruction for diplomats to be on alert.

"As we did with all of our missions overseas, in advance of the Sept. 11 anniversary and as we do every year, we did evaluate the threat stream and determined that the security was appropriate for what we knew," State Department spokeswoman Victoria Nuland said.

Many are also pointing out that just one day before the attack, an al Qaeda leader Ayman al- Zawahiri called for Libyans to rise up against Americans over the recent killing of a high-ranking al Qaeda official.

"So one day before the storming of the embassy in Libya, Zawahiri releases a tape calling for vengeance, calling for jihadists to rise up. That's exactly what happened," CBN News Terrorism Analyst Erick Stakelbeck said.

The State Department stressed there was no advance warning or intelligence to suggest a threat in Libya that would warrant boosting security.

House Intelligence Committee member Adam Schiff, D-Calif., said the focus now "has to be on finding out who is responsible and bringing them to justice."