LIVERMORE -- With its leadership team in disarray after the sudden death of one high-ranking official and the unannounced departure of a second, Lawrence Livermore Lab appears to be in some turmoil at a critical point for one of the federal government's top research labs.

The lab made no public announcement, but notified workers Thursday that one of its leading managers, Tomas Diaz de la Rubia, the deputy director of Science and Technology, was leaving.

"After 23 years he stepped down to pursue other opportunities," said Lynda Seaver, the lab's deputy director of media and communications.

Diaz de la Rubia, 52, has been on an unspecified leave from the lab for at least the past two weeks, according to the lab. Diaz de la Rubia didn't return calls seeking comment. "He will stick around to transfer other responsibilities," Seaver said, but didn't have other details about Diaz de la Rubia's departure.

The lab community is still reeling from the death of Allan Snavely, the lab's chief technical officer who died of a heart attack after biking up Mt, Diablo on July 14. Snavely had just joined the lab's super computer department in April.

Snavely is best known as co-creator of UC San Diego's Gordon supercomputer. "Flash Gordon" is reportedly the world's most powerful supercomputer to use flash memory, allowing it to store and process data at lightning speeds.The loss of the two key figures comes at a time when rumors of trouble at Lawrence Livermore are rampant at the lab and in the community, with talk of an ongoing investigation into possible employee misuses of expense and travel accounts, as well as of the possible departure of another key lab official.

Seaver said she had no knowledge of any investigations taking place.

John Belluardo, the public affairs director for the Livermore site office of the National Nuclear Security Administration, said the "office does not comment as a matter of policy on potential or ongoing investigations conducted by law enforcement agencies or internal investigations involving laboratory contractors or federal personnel."

Fueling the rumors in part is a blog spot created by lab workers that is rife with anonymous postings on Diaz de la Rubia's sudden departure, and speculations on why lab officials took weeks to comment on his status.

Adding fuel to the fire, two weeks ago the lab sent out an email to employees reminding them about the rules for business travel. The July 17 note reminded workers that conferences and travel are paid for with "taxpayer dollars." The email went on to say that employees "should ensure that federal funds are used solely for the purposes that are appropriate, cost-effective, and important to the core mission of the DOE... "

The turmoil comes just weeks after the lab reclaimed the world's top honor for the fastest supercomputer and marked a major milestone at the National Ignition Facility, the world's largest super-laser.

On June 18, the lab's supercomputer Sequoia helped the U.S. reclaim the honor as world's fastest computer when it clocked 16.32 sustained petaflops, which is a quadrillion calculations per second. It would take 7 billion people on Earth 300 years, calculating with a hand calculator 24 hours a day, 365 days a year to do what Sequoia can do in an hour.

Following that milestone, the NIF achieved a record-breaking laser shot on July 5. The laser system used 1,000 times more power than the United States uses at any moment and the energy in the shot was 100 times more than any other laser can produce, according to published reports.

Contact Robert Jordan at 925-847-2184. Follow him at Twitter.com/robjordan127.