NEW YORK -- WNBC.com's Jonathan Dienst has learned a contract worker is accused of stealing nuclear secrets from the Oak Ridge National Lab in Tennessee.

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Video: Contractor Accused Of Stealing Nuclear Secrets

PDF: Read The Indictment

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Investigators said the worker, 67-year-old Roy Lynn Oakley, wanted to sell the secrets to a foreign country.

Investigators are calling the theft a serious breach of security at one of the country's most important nuclear research labs. Officials said there was serious concern the documents could have fallen into the hands of enemy states or even terrorist organizations.

NewsChannel4 has learned that among the materials allegedly stolen was classified information about the uranium enrichment process. Officials familiar with the case said Oakley will face charges including violations of the Atomic Energy Act.

Oakley worked as an escort at East Tennessee Technology Park, located on the Oak Ridge reservation. Officials said his contracting job was to escort visitors to and from offices at the lab. Officials said Oakley also performed maintenance work at the facility.

Sources said it is unclear how a low-level contract worker was able to obtain some of the nation's highly guarded nuclear documents.

Spokesmen at the Justice Department, FBI and Department of Energy declined to comment.

An announcement on the security breach and resulting criminal charges are expected later Thursday.

WNBC.com has learned FBI agents and Department of Energy investigators have searched the Oakley's home in the investigation, which began several months ago.

Officials said Oakley was charged as a result of a later sting in which investigators posed as representatives of a "foreign government" willing to pay for the nuclear research materials.

Officials did not identify to which country Oakley allegedly thought he was selling the secrets.

Sources said money, not ideology, was the motive. The Oak Ridge National lab, located in eastern Tennessee, near Knoxville, was established in 1943.

The lab was part of the government's secret Manhattan Project -- designed to build the first atomic bomb.

It is the Energy Department's largest science and energy laboratory.

Oakley is expected to be arraigned in federal court in Knoxville Thursday.