The headquarters of Sweden’s SAPO intelligence service was evacuated on Friday and eight people were hospitalized with “symptoms” after a gas leak, the nature of which authorities did not specify, the France-Presse and Agerpres agencies reported.

Footage taken at the scene shows police in gas masks, as well as ambulances around the SAP headquarters.

“At around 1:00 p.m. there were indications that there was a dangerous substance at the SAPO headquarters,” Patrik Soderberg, chief medical officer of the health service in the Stockholm region, told AFP.

“A total of eight people were taken to hospital with symptoms,” the Stockholm administration said in a statement, adding that “the cause of the gas leak is unclear.”

SAPO spokeswoman Karin Lutz told AFP that “measures were taken and emergency services were dispatched to the scene” after being alerted.

The Scandinavian kingdom, which is on the brink of ending its NATO membership following Russia’s invasion of Ukraine two years ago, is on high alert, paying particular attention to a possible Russian threat to its security.

The spokeswoman confirmed that the SAP headquarters was “partially evacuated”, but refused to say more.

The police, for their part, indicated that a perimeter of “approximately two hundred meters” around the building was blocked due to “a possible gas leak.”

Some of those hospitalized are police officers who “sense a strong odor when they arrived” at the scene, police said.

Around 4:30 p.m., the police announced the completion of the operation. Later, they reported that an investigation had been opened into the “injuries”.

According to newspaper Aftonbladet, several witnesses said they smelled a smell similar to paint and that residents of the area were told to close their windows.

On Wednesday, the Swedish special services warned about potential threats to the country’s security from Russia, as well as China and Iran.