The FBI is backing away from an advisory sent out earlier this week warning police that al-Qaida cells may use car and truck bombs in southern California, Chicago and New York.
NBC News' Pete Williams reported that the agency will issue a revised notice on Friday.
Officials stressed at the time that the warning was based on uncorroborated intelligence.
The bulletin, which warned that terrorists could use fuel tankers in assaults on the three cities, was distributed Tuesday via a computer network by FBI officials in Los Angeles to law enforcement agencies primarily in California, said FBI spokeswoman Laura Eimiller.
The notice was based on a single source of unknown credibility containing information that had not been corroborated. However, the source has since backed off the statement that led to the notice, an official told NBC News.
On Thursday, Eimiller had noted that FBI officials often notify police of possible threats, regardless of how accurate the information might be.