LONDON (AP) — One security expert says British officials must have been hearing something that caused concern, in order for them to raise the country’s terror threat level today to “severe,” the second-highest level.

Officials said they weren’t responding to any specific threat. But Christian Leuprecht, a security expert at the Royal Military College of Canada and Queen’s University, says there must have been “something more concrete than, ‘Oh, we’d better be careful.'” Otherwise, he says, “you would see everyone in the West do this.”

And in fact, the White House says it doesn’t expect the U.S. to bump up its terrorism threat warning level. A spokesman says the U.S. is in touch with British officials, and monitoring the threat of foreigners fighting alongside militants in Iraq and Syria who could then travel back to their home countries. New York’s police commissioner also says the city is closely following developments overseas, but that there’s “no specific credible threat” to the city.

British Prime Minister David Cameron today said the extremist threat posed by the Islamic State group is more dangerous than even the threat from al-Qaida. He says the group is “effectively a state run by terrorists.”

Intelligence and security services now believe around 500 Britons have gone to fight in Syria and potentially Iraq.

%@AP Links

179-a-15-(Josh Earnest, White House press secretary, at news conference)-“channels as well”-White House press secretary Josh Earnest says senior officials are talking to U.S. allies about the threat. (29 Aug 2014)

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181-a-11-(Trevor Ford, 54-year old business owner from Essex, England, in AP interview)-“spoke about it”-Trevor Ford is a business owner who lives in Essex, Angland, and says the terror threat has his family trying to stay out of London. (29 Aug 2014)

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APPHOTO LON819: British Prime Minister David Cameron delivers a report to the media in Downing Street, London, Friday Aug. 29, 2014. Britain’s Home Secretary Theresa May has announced that UK’s terror threat level is being raised from “substantial” to “severe” on Friday, meaning that a terrorist attack is considered highly likely. (AP Photo/Facundo Arrizabalaga, Pool) (29 Aug 2014)

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