STOCKHOLM (AP) — Swedish authorities said Tuesday that two more people have been arrested on suspicion of spying, including one accused of “gross illegal intelligence activities against Sweden and against a foreign power.”

In a brief statement, Sweden’s Prosecuting Authority said the arrests were made Tuesday morning. It did not identify the other country involved.

Sweden’s security agency said the operation, which included house searches, was carried out with the assistance of the police and the Swedish Armed Forces. The spy agency said a probe “has been ongoing for some time.”

The arrests were made early in the morning in the Stockholm area. No details about those arrested was given.

Fredrik Hultgren Friberg, a spokesperson for Sweden’s domestic security service, known by its acronym SAPO, told the Aftonbladet tabloid that “there was a need to quickly arrest the suspects.”

A spokesperson for Sweden’s Armed Forces told Aftonbladet that they had “supported SAPO with two helicopters.”

The Prosecuting Authority stressed the case was not linked to two Iranian-born brothers who were charged earlier this month in Sweden with aggravated espionage for allegedly spying for Russia.

On Nov. 11, Sweden charged the two naturalized Swedes for allegedly spying for Russia and its military intelligence service GRU for around a decade, from 2011 to 2021.

One of the men worked for Sweden’s domestic intelligence agency. Both have denied any wrongdoing.