The British ambassador to the United States said on CNN Sunday that his country’s security services are close to identifying the killer of American journalist James Foley.

Speaking to host Candy Crowley on "State of the Union," Sir Peter Westmacott said that “we’re not far away” from finding the jihadist who beheaded the American photojournalist.

“We’re putting a lot into it, and there are some very sophisticated technologies — voice identification and so on — which people can use to check who these people are,” he said.

He added that upwards of 500 Brits could have gone to fight for ISIS.

Meanwhile, some UK media outlets, including the Sunday Times, are reporting that rapper Abdel-Majed Abdel Bary is a suspect. Yahoo News reports that Bary left his west London home last year to fight in Syria’s civil war, and that he said he “was leaving everything for the sake of Allah.”

Westmacott wouldn’t give further detail on the investigation.

British Prime Minister David Cameron cut short his vacation last week when the news of Foley’s beheading broke.