A cyber attack has hit Spanish companies including Cadena SER radio, Spain’s National Security Department said on Monday.

The virus affected Cadena Ser’s local broadcasts, although national output was not affected, said the broadcaster which has a chain of local and countryside stations.

“We have been recommended not to work on our computers in a network environment,” a source at the station told Reuters.

The National Security Department did not identify any other victims of what it said were ransomware attacks against a number of companies.

Such an attack typically locks an infected computer system until payment, usually in the form of cryptocurrency, is sent to the hacker.

A number of businesses including airport operator Aena and KPMG Spain took to Twitter to say they had not been affected, though Aena said it had taken preventive measures.

Technology media outlet Xataka, online news portal El Confidencial and daily El Mundo said Spanish data company Everis was also affected and had sent its employees home with instructions for turning off devices. A spokeswoman at Everis declined to comment.