By MARK MAZZETTIJAN. 19, 2016

WASHINGTON — Intelligence officials reviewing emails on former Secretary of State Hillary Clinton’s private computer server have found information they consider to be of a higher level of classification than “top secret,” according to a letter sent to lawmakers last week by the intelligence agencies’ inspector general.

The letter, dated last Thursday, says that some of the information in Mrs. Clinton’s emails has been determined to be “top secret/SAP.” That designation is usually given to information about “special access programs” — often intelligence-gathering programs and other secret programs run by the Pentagon and the C.I.A. — that are among the government’s most closely guarded secrets.

The letter to Congress, from I. Charles McCullough III, the inspector general for the nation’s intelligence agencies, provides no specifics about the classified material. It is not clear from the letter whether Mrs. Clinton sent or received the emails, nor how many contained the classified information.

Last year, the intelligence agencies found after the fact that two of Mrs. Clinton’s emails contained information that was “top secret.” The State Department disputed the determination, but it prompted an F.B.I. investigation into whether such information had been mishandled in connection with Mrs. Clinton’s account. By law, classified information is not allowed outside government computer servers. The government has said that Mrs. Clinton is not a subject of the investigation.

The letter was sent to the Republican chairmen of the Senate Intelligence and Foreign Relations Committees. It was not made public.

“This is the same interagency dispute that has been playing out for months, and it does not change the fact that these emails were not classified at the time they were sent or received,” Brian Fallon, a spokesman for the Clinton campaign, said.

“It appears that this may still revolve around a State Department employee forwarding a published news article about the drone program,” he said. “If so, it would further reinforce how absurd it is to suggest that Secretary Clinton did anything wrong.”

John Kirby, the State Department spokesman, said on Tuesday that the department “is focused on and committed to releasing former Secretary Clinton’s emails in a manner that protects sensitive information.”