Rio de Janeiro (CNN) A judge has ordered WhatsApp service be reinstated across Brazil, granting an appeal by the messaging app's parent company, Facebook.

It unclear when the WhatsApp service will be available for users in Brazil. It's expected to be restored once operators are notified of the judge's decision.

A regional judge on Monday ordered all telephone operators in Brazil to block WhatsApp, the popular messaging app, for failing to turn over data as part of an ongoing drug trafficking investigation.

The app ceased to function that afternoon, frustrating Brazilians who use its free-calling functions regularly.