Two more people have been detained in connection with the arson attack on a Czech optics and drone factory last month, authorities said.
No injuries were reported after an industrial company about 120 km (75 miles) east of Prague caught on fire on March 20, which a previously unknown pro-Palestinian activist group claimed responsibility for.
Czech authorities have previously announced five detentions, including of an Egyptian and a U.S. citizen, since the fire that targeted a building used by the Czech defence group, LPP Holding.
Polish prosecutors said on Wednesday that two Polish citizens were also detained in connection with the case.
Czech police and prosecutors said another person was detained on Saturday. A further individual was also detained in Bulgaria on Friday and police said their extradition will be requested.
Both were foreign nationals, Czech authorities said.

The group that claimed responsibility for the attack has said in a statement online that the targeted company was developing weapons for Israel. LPP Holding announced plans to cooperate with Israeli group Elbit Systems ESLT.TA in 2023, but says those plans were never implemented.
The company develops and makes products for civilian and military use, such as drone technologies used by Ukraine’s armed forces in the fight against the Russian invasion.
Interior Minister Lubomír Metnar said “the incident may be related to a terrorist attack.”
The fire was extinguished by firefighters and police said there was no danger to the public. It was not immediately clear what was inside the warehouse that was on fire.
LPP Holding had previously said it was planning to open a center to develop and produce drones and train personnel in cooperation with Israeli Elbit Systems, a military technology company.
