WASHINGTON — The C.I.A. scrambled on Wednesday to assess and contain the damage from the release by WikiLeaks of thousands of documents that cataloged the agency’s cyberspying capabilities, temporarily halting work on some projects while the F.B.I. turned to finding who was responsible for the leak.

Investigators say that the leak was the work not of a hostile foreign power like Russia but of a disaffected insider, as WikiLeaks suggested when it released the documents Tuesday. The F.B.I. was preparing to interview anyone who had access to the information, a group likely to include at least a few hundred people, and possibly more than a thousand.

An intelligence official said the information, much of which appeared to be technical documents, may have come from a server outside the C.I.A. managed by a contractor. But neither he nor a former senior intelligence official ruled out the possibility that the leaker was a C.I.A. employee.

The officials spoke on the condition of anonymity to discuss an ongoing investigation into classified information. The C.I.A. has refused to explicitly confirm the authenticity of the documents, but it all but said they were genuine Wednesday when it took the unusual step of putting out a statement to defend its work and chastise WikiLeaks.