Investigators are obscuring the facts surrounding Sergei Magnitsky’s death in a Moscow prison, the tax lawyer’s former employer said Tuesday after Investigative Committee chief Alexander Bastrykin indicated that there was no evidence of physical or psychological abuse in the case.

Those statements are “proof of a high-level, state-sponsored cover-up,” Jamison Firestone, co-founder of law firm Firestone Duncan, said in an e-mailed statement.

Firestone says Magnitsky, who died last November, was punished for testifying against police officers involved in a $230 million tax-rebate scam.

But Bastrykin said there was no reason to believe that his death was connected to the activities of officials prosecuting his criminal case.

“Not in one of his statements did he complain about pressure or the use of illegal investigation methods,” Bastrykin said in an interview published in Rossiiskaya Gazeta on Tuesday.

Magnitsky, arrested in November 2008, died of toxic shock and heart failure after 358 days in pre-trial detention, according to a statement from the Foreign Ministry posted on the American Chamber of Commerce in Russia web site.

Firestone’s statement cites two of Magnitsky’s 450 official complaints, in which he described “physical and psychological pressure” and said his prosecution was “a repressive measure to punish me.”

Investigators are continuing a “calm and objective” investigation of Magnitsky’s case, Bastrykin said.