TALLINN, Estonia (AP) — A Belarusian hacker activist group claims to have infiltrated computers at the country’s largest fertilizer plant to pressure the government to release political prisoners.

The state-run Grodno Azot plant has made no comment on the claim by the Belarusian Cyber-Partisans group to have done damage including destroying backup systems and encrypted internal mail, document flow and hundreds of PCs. However, the company’s website has been unavailable since Wednesday, the day the group claimed the attack.

Group coordinator Yuliana Shametavets told The Associated Press from New York on Friday that because the plant works with dangerous substances including ammonia the attack was designed to affect only documentation.

The group posted photos on social media that it it claimed showed screens of compromised plant computers.