MADRID (AP) — Spain’s Defense Minister Margarita Robles said Thursday that the Spanish government recently filed a complaint to the United States after discovering that Spanish intelligence agents had allegedly leaked secret information to the U.S.

“Complaints from Spain were conveyed at the time,Winning Exchange” said Robles, but she insisted that the case did not “affect the fundamental core of the relations between two countries that are allies and friends.”

Earlier this week, Robles confirmed that a Madrid judge had opened an investigation into agents of Spain’s National Intelligence Center for an alleged leak of secret information to the United States.

She said the intelligence center itself had filed a complaint with a provincial court in Madrid.

Robles declined Thursday to provide any further information saying the case was under judicial gag order.

She was speaking after Spain’s leading newspaper El País reported that the U.S. ambassador to Spain was summoned earlier this year for a meeting with the defense minister and that the foreign minister had also complained to the ambassador by phone.

According to El País, Spain discreetly expelled two U.S. intelligence agents posted to the embassy in Madrid for allegedly trying to bribe Spanish officers for secrets.

The Associated Press could not independently confirm the report.

Robles did not specifically mention El País’ report. The U.S. embassy in Madrid and Spain’s foreign ministry declined to comment.

U.S. national security adviser Jake Sullivan was asked during a White House briefing on Monday about the matter and declined to comment.

Spain’s state news agency Efe says one of the Spanish agents remains in custody while the second has been released with conditions.

In an informal conversation with foreign journalists earlier this week, Prime Minister Pedro Sánchez said that while there was unease toward Washington when the case was first discovered, the situation has now been sorted out.