Moscow ? Scores of plainclothes police searched for several hours Saturday through the headquarters of the Russian oil giant Yukos, beleaguered by a $3.4 billion back taxes claim.

The Interfax news agency reported that the search ended after the officers removed several boxes of documents. But company spokesman Hugo Erikssen said it was not clear what was taken away and could not confirm earlier reports that police had intended to take computer servers.

No Yukos officials were in the building during the raid.

“Why they had to come on a weekend … that’s a question we’d like to know,” the spokesman said.

The move came a day after a Moscow court refused to unfreeze the company’s assets, making it impossible for the company to sell property in order to pay the back taxes bill.

Prosecutors said, however, that Saturday’s actions were connected to a criminal fraud and tax evasion case “against structures controlled by Yukos,” news agencies said. The reports said the matter was separate from the fraud and tax evasion cases pending against Yukos ex-CEO Mikhail Khodorkovsky and an associate.

The Prosecutor-General’s Office refused to elaborate, but the statement appeared to refer to allegations of tax-dodging by Samaraneftegaz, Yukos’ third-largest operating unit.

Yukos also likely faces claims beyond the $3.4 billion that a court upheld this week. News reports said the Tax Service was seeking another $3 billion for 2001 back taxes.

Yukos has said it faced bankruptcy if it could not sell assets to pay the tax bill and stagger the payments.