The Russian authorities have extended their investigation into the death of Aleksei A. Navalny and have again blocked the opposition leader’s mother from seeing his body, Mr. Navalny’s spokeswoman said on Monday.
Mr. Navalny was regarded as the most vocal critic of President Vladimir V. Putin in Russia. His sudden death in prison, which was announced by the Russian authorities on Friday, shocked his supporters and raised immediate suspicions about the circumstances.
The cause of Mr. Navalny’s death has not been established. Mr. Navalny’s mother and lawyers have been trying to see his body since Saturday, calling for it to be released so that they can carry out an independent analysis. They tried again on Monday morning but were not allowed in, according to Kira Yarmysh, Mr. Navalny’s spokeswoman.
“One of the lawyers was literally pushed out,” Ms. Yarmysh said in a post on the social media platform X, adding in another post, “They lie, buy time for themselves and do not even hide it.”
Russian investigators initiated an inquiry into the causes of Mr. Navalny’s death shortly after it was reported, a procedural move that allows them to hold the body for longer than normal. Ms. Yarmysh said that investigators told Mr. Navalny’s mother on Monday that the investigation had been extended.
Ivan Zhdanov, the head of Mr. Navalny’s anti-corruption foundation, said that the delay meant that Russian officials were “cleaning up traces of their crime.”
“They are waiting for the wave of hatred and rage toward them to calm down,” Mr. Zhdanov said in a post on Telegram, a messaging app.
The Kremlin spokesman, Dmitri S. Peskov, rejected any suggestion of impropriety on Monday, saying that the investigation into Mr. Navalny’s death has been continuing “in accordance with the Russian law.”
More than 50,000 people have signed a petition to Russian investigators demanding the release of Mr. Navalny’s body, a campaign initiated by a Russia-based human rights group, OVD-Info.
Mourners have brought flowers to makeshift memorials across Russia, paying tribute to Mr. Navalny with an act of grief that has also served as a form of protest in a country where even the mildest dissent can risk detention.
The Russian authorities have tried to tamp down the scale of public mourning over Mr. Navalny’s death. Flowers have been quickly removed from memorials and the police have detained hundreds of people.