Russian opposition politician and former lawmaker Dmitry Gudkov was released from custody on June 3 without being formally charged.
Gudkov was detained in Moscow two days earlier over an allegedly unpaid debt on a rented property dating from several years ago.
A court had been expected to consider the terms of his pretrial detention, but the hearing did not take place.
The politician was legally required to be released on the evening of June 3 as 48 hours had elapsed since his detention.
Although no charges were brought against him, he remains a suspect in the case.
Gudkov is a former member of the lower chamber of Russia’s parliament, the State Duma.
Kremlin critics says the authorities have been stepping up a campaign of intimidation against dissent ahead of parliamentary elections in September, an allegation rejected by officials.
Also on June 3, Russian authorities opened a criminal case against Gudkov's father, Gennady, a former State Duma deputy and Kremlin critic who lives in Bulgaria, over ammunition allegedly found at his apartment in Russia, local media reported.
The state-run TASS news agency said that law enforcement officers found 50 cartridges for a pistol during a search of Gudkov's apartment.
They also found an expired permit for the weapon, the agency said.
According to media reports, the cartridges were found during a search conducted in the case involving his son.
There was no official confirmation of the criminal case from officials.