The FSB raided the premises of two Roscosmos facilities Friday morning, Sputnik News reported. It was suspected that an employee of the Central Research Institute of Machine Building (TSNIIMASH), near Moscow, was responsible for leaking secrets about the technology, which the United States reportedly fears it's still utterly incapable of countering.
Roscosmos confirmed that Kudryavtsev has been detained. They've also created a commission to investigate TSNIIMASH and rebutted reports that another employee has been arrested.
Roscosmos spokesman Vladimir Ustimenko on Monday confirmed that the organization has opened an internal probe which will start investigative work later in the week, according to the Daily Mail.
Kudryavtsev claimed he's not guilty of the charge of treason, according to statements from the scientist's son.
Around 10 people were believed to have cooperated with intelligence agencies from unknown Western countries.
Russia's hypersonic missiles were revealed by Russian President Vladimir Putin in a speech in March in which he described them as "invincible." They're also said to be capable of destroying an aircraft carrier and striking anywhere in the world. Some are reportedly in service already, but most are believed to be still in development.
The US Department of Defense is now seeking $20 million from Congress to pay for the development of its own hypersonic weapons.