The United States has no indication that a couple who killed 14 people in California were part of a wider cell or that they planned more attacks, U.S. Attorney General Loretta Lynch said on Wednesday.
Speaking to reporters in London, Lynch said the radicalization of the couple seemed to have been going on for some time.
But she added: "At this point in time we do not have an indication that these two people were part of a larger cell or group."
"We do not have an indication that they were planning specific things beyond this attack although that information is still evolving," she continued.
Lynch's comments came as FBI Director James Comey said Tashfeen Malik, 29, and her husband, Syed Rizwan Farook, 28, were radicalized at least two years ago and had discussed attacks as early as 2013.
Comey told the Senate Judiciary Committee that investigators believe Farook and Malik, were radicalized even before they began their online relationship and that Malik held violent ideological views before she arrived in the U.S. last year. He told the panel that the two "as early as the end of 2013 were talking to each other about jihad and martyrdom before they became engaged and married."
Malik and Farook stormed a gathering of his work colleagues in San Bernardino, California, last Wednesday, opening fire with assault-style rifles.
They were killed a few hours later in a shootout with police.
"We are trying to learn everything we can about both of these individuals, as individuals and as a couple, to determine why they chose that location, that event, that particular place to vent their rage," Lynch said.
"We are essentially digging into their lives as far back as we can," she added. "Our view is that the radicalization had been going on for some time, but it's really too early to tell at this point what was the genesis of it for either of them."