Law enforcement agencies started a check at Detention Center No. 1, dubbed Matrosskaya Tishina, on Wednesday after the sudden death of a lawyer being held there.

Prosecutors are looking into whether Sergei Magnitsky, 37, who apparently died of heart failure Monday, was denied medical treatment, the Prosecutor General’s Office said in a statement.

Magnitsky, a partner with the Firestone Duncan law firm, had been accused of being directly involved in developing and executing a scheme in which William Browder, head of the Hermitage Capital investment fund, purportedly evaded more than 100 million rubles ($3.25 million) in taxes in 2002.

Hermitage has called the charges politically motivated, saying they were laid because of the firm’s claims of corruption in the Interior Ministry.

The ministry’s investigative committee said Tuesday that Magnitsky died of apparent toxic shock and heart failure at Mattroskaya Tishina, where he was taken for medical attention. Magnitsky was the only suspect arrested in the case, although Browder was recently put on Russia’s international wanted list.

Magnitsky had been held for nearly a year without trial, most recently in the Butyrskaya jail, where he complained of inhumane conditions. Both facilities are run by the Federal Prisons Service.

It was not immediately clear why the prosecutors decided to inspect Matrosskaya Tishina.

Magnitsky’s lawyer, Dmitry Kharitonov, told The Moscow Times that he would request that criminal charges be filed in connection with the death. Magnitsky was diagnosed with pancreatic problems and was repeatedly denied medical attention.

A spokeswoman for the ministry’s investigative committee said Tuesday that Magnitsky had not complained about his health while in detention. An autopsy will be performed.

The Public Chamber, a government oversight body, said the investigator responsible for the case should be held accountable. “The investigator who allowed the suspect’s death — without paying attention to his health, and probably without providing timely access to a doctor — must carry personal responsibility,” said lawyer Anatoly Kucherena, head of the chamber’s committee to oversee the activities of law enforcement agencies, Interfax reported.