Jake Tapper contributed to this report. Democratic presidential hopeful Barack Obama was put under the protection of the United States Secret Service Thursday, the earliest in an election cycle that the Secret Service has placed a presidential candidate under its protection, the Secret Service said. Two sources said that security concerns, including large crowds and unspecified threats against the candidate, were the reasons for the security detail. But a Department of Homeland Security official said there is no known viable threat against the senator "at this time." The FBI confirmed that there was no specific threat against Obama. According to the DHS, the candidate’s campaign requested the security detail, an advisory committee approved that request and the Secret Service initiated the protective detail. "Yes, we can confirm we are protecting Senator Obama," U.S. Secret Service spokesman Darrin Blackford said. Click Here for Full Blotter Coverage. "We are not going to discuss the nature of the protective detail now that it has been put into place," another Secret Service spokesman said. Robert Gibbs, the spokesman for Obama, referred all questions to the Department of Homeland Security and the U.S. Secret Service. In February, the candidate’s wife was asked on "60 Minutes" if she worried about her husband’s safety now that he had embarked on his presidential campaign. "I don’t lose sleep over it because the realities are that, you know, as a black man, you know, Barack can get shot going to the gas station," she responded. "You can’t make decisions based on fear and the possibility of what might happen. We just weren’t raised that way." The Secret Service has protected major party candidates ever since New York Sen. Robert Kennedy was gunned down in June 1968. Candidates qualify for Secret Service protection after a committee approves someone as a major candidate. That five-member committee includes the speaker of the House, the House minority leader, the Senate majority and minority leaders and one additional legislator selected by those committee members. It is chaired by the Department of Homeland Security. The criteria normally include an announcement of candidacy, prominence, major party affiliation, fundraising and matching funds. Some of those criteria may not be required at this early date. According to a recent report in Newsday, Secret Service Director Mark Sullivan said he expected to spend $88.5 million next year for bodyguards and bomb-sniffing dogs to protect the 2008 presidential candidates. That’s on top of this year’s $21.4 million, bringing the total for this election cycle to $106.6 million, up from the $73.03 million spent when President George W. Bush and Vice President Dick Cheney ran for re-election in 2004. Agents recently informed Democratic candidate Sen. Hillary Clinton’s neighbors in Chappaqua, N.Y., that they were boosting security, according to a report in the New York Post. Clinton receives Secret Service protection since she is a former first lady. This post has been updated.