-year-old staunch critic of President Vladimir Putin, was on a ventilator and in a coma, and that the Omsk Emergency Hospital was now full of police officers, the BBC reported.
She said doctors were initially ready to share any information but were now saying the toxicology tests were delayed and were "clearly playing for time, and not saying what they know".
Navalny is in the intensive care unit.
The hospital's chief physician Alexander Murakhovsky earlier told TASS News Agency that he was in serious condition, adding that doctors were yet to diagnose his case.
Addressing reporters, Anatoly Kalinichenko, deputy chief physician, said: "There are diagnoses that have been ruled out or are in the process of confirmation. (Doctors) are holding consultations. We will decide on the diagnosis later in the day.
"Symptomatic treatment (is currently being conducted)."
Kalinichenko added it was not yet certain if Navalny was poisoned.
Navaln has made a name for himself by exposing official corruption, labelling Putin's United Russia as "the party of crooks and thieves", and has served several jail terms.
( With inputs from IANS )
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