Japanese police have raided the offices of a cult once known as Aum Shinrikyo, a day after its ex-leader lost his last appeal against a death sentence.
Asahara was originally sentenced in 2004
Officials entered 25 facilities associated with the cult looking for illegal activities by members.
Shoko Asahara was convicted in 2004 of masterminding a 1995 gas attack on the Tokyo subway in which 12 people died and hundreds were injured.
The cult changed its name to Aleph in 2000 and has renounced violence.
But it is still heavily monitored by police.
1955 - Born in Yatsushiro, real name Chizuo Matsumoto
1987 - Starts Aum Shinrikyo
1994 - First sarin attack
1995 - Tokyo subway attack
1996 - Goes on trial
2004 - Trial ends
Security officials said they wanted to check for any unexpected reaction to the Supreme Court's decision.
"Our aim is to prevent any illegal activities by cult members in response to the confirmation of Asahara's death sentence," an agency official told Reuters news agency.
"Of course, we basically want to put the public's mind at rest."
The cult leader, a former acupuncturist, was sentenced to death in February 2004 after a trial lasting eight years.
He was also found guilty of other charges including plotting a 1994 gas attack in the central Japanese city of Matsumoto that killed seven people.
'Genius of meditation'
Altogether, 12 cult members have been sentenced to death, but none of the sentences have yet been carried out.
Japan does not announce the dates of executions and they could happen at any time.
Last month, a court upheld the death sentence for the cult's alleged second in command, a chemist who oversaw the development of the nerve gas.
Before the attacks, Aum Shinrikyo had thousands of members, many of them educated and wealthy, who embraced Asahara's violent apocalyptic teachings.
In its new form as Aleph, it still considers Asahara a "genius of meditation" but says it cannot approve of Aum's activities under his leadership and no longer considers him its guru.