Police in Poland have arrested two men in connection with explosions at Ikea stores in several European countries, they said Saturday.

The two men, both age 39, are accused of trying to force Ikea to pay a ransom of six million euros (U.S. $8 million).

They were arrested after a joint operation involving several hundred officers from Poland’s Central Investigation Bureau and investigators from other countries, police said in a statement.

There were eight explosions of increasing strength between May and early September, at large stores in France, Belgium, Holland, Germany and the Czech Republic, police said.

Initially the explosions were treated as individual cases in the countries where they occurred, but police now believe the plot was orchestrated from Poland, the statement said. The suspects made use of technology and traveled large distances to try to avoid detection in Poland, it added.

The men have been accused of racketeering and extortion offenses, as well as endangering people’s lives.

One of the suspects, identified as Adam K., has no previous criminal record, is fluent in four languages and previously worked as a manager at several large corporations, giving him technical expertise, police said.

The second suspect, identified as Nicholas G., has a record of past drug offenses, police said.

CNN’s Per Nyberg contributed to this report.