(CNN) -- A liberal Democratic congressman who came under fire for a lewd photo that briefly appeared on his Twitter account over the weekend told CNN Wednesday that he did not post the image. Democratic Rep. Anthony Weiner spoke to CNN's Wolf Blitzer a day after a contentious exchange with reporters in which he refused to directly answer any questions about the picture. On Wednesday he said he had hired a law firm to look into the matter. But he declined to directly answer whether he appeared in the photo. "Photos can be manipulated. Photos can be of one thing and changed to something else. We're going to try to get to the bottom of what happened," he said. The photo showed the lower body of a man wearing underwear.
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NEW: Twitter e-mails members of Congress about account security
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Weiner says he did not post a lewd photo and has hired a firm to investigate
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On Tuesday he had a heated exchange with reporters
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A conservative blogger who broke the story wants an investigation
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