(FILES) -- Russian lawyer Sergei Magnitsky, who had been investigating corruption among police and tax officials, was arrested on fraud charges and died in jail in 2009, allegedly after a beating and being denied medical care. (HO/AFP/Getty Images)

The Obama administration added no names Friday to a list of Russians accused of complicity in the death of a lawyer whose case has become both an international symbol of human rights abuses in Russia and a flashpoint in the volatile U.S. relationship with Moscow.

The State Department had been widely expected to add to the blacklist of 18 Russian officials subject to visa bans and asset freezes as part of a review required by Congress last year. More than 10 Russians were reported to be under scrutiny, including a high-ranking prosecutor.

The mandated review named for Russian lawyer Sergei Magnitsky was submitted Friday, but no list of alleged wrongdoers came with it. Magnitsky, who had been investigating corruption among police and tax officials, was arrested on fraud charges and died in jail in 2009, allegedly after a beating and being denied medical care.

Congressional officials said the decision is a complete turnabout after months of public and private signals to Congress that the administration was preparing allegations against several Russians.

State Department spokeswoman Jen Psaki said new names were not mandatory now, and that more officials could be added at any time. She would not directly address whether political sensitivities drove the decision.

“We’ve always said we would continue to consider future names, which we are doing now,” Psaki said. “There isn’t a deadline.”

She gave no estimate of when any names might be added.

Sen. Bob Corker (R-Tenn.), the top Republican on the Senate Foreign Relations Committee, called the omission of new names “a strange decision” and demanded an explanation in a letter to Secretary of State John F. Kerry on Friday.

The new report comes at a delicate time.

The United States and Russia are partners in fragile diplomatic gambits involving the destruction of Syrian chemical weapons and the temporary freezing of Iran’s nuclear program. There is already friction between Washington and Moscow over Russia’s housing of former National Security Agency contractor Edward Snowden and over American suggestions that Russia is forcing its will on neighboring Ukraine.

“We have a multifaceted relationship with Russia that involves important cooperation in areas of mutual interest,” Corker wrote.

“I understand the administration may be concerned that an expansion of the Magnitsky list could undermine that cooperation,” but that doesn’t change the fact that the law was passed and must be followed, Corker concluded.

The administration opposed the sanctions review backed by a bipartisan slate of human rights advocates in Congress but went along with it as part of a larger legislative bargain a year ago. Infuriated, Russia retaliated with sanctions of its own and a ban on U.S. adoptions of Russian children.

Russian lawmakers described the U.S. legislation as interference in its internal affairs.

“The lack of new names on the list is very disappointing,” said Rep. Jim McGovern (D-Mass), a sponsor of the Magnitsky law.

“I am looking forward to the day when the Magnitsky law will become obsolete because the climate of impunity no longer prevails inside Russia. But today is not that day.”

The Obama administration insists it maintains pressure on Russia to improve human rights and answer questions about Magnitsky’s death.

The White House announced this week that the U.S. delegation to the February Olympics in Sochi, Russia, will include no high-ranking officials but will include several openly gay athletes and activists. The snub’s connection to recent anti-gay laws in Russia was obvious.

“I think the delegation speaks for itself,” President Obama said at a news conference Friday. “We judge people on how they perform, both on the court and off the court, on the field and off the field. And that’s a value that I think is at the heart of not just America but American sports.”

Karen DeYoung contributed to this report.