Niantic’s popular smartphone game, Pokemon Go, is currently hiding a secret that apparently remains undiscovered. Speaking to GamesRadar, Niantic CEO John Hanke teased that Pokemon Go will "always" have secrets embedded in the app because the studio is continually adding new secrets.

"There’s one out there right now and we’ll see how that plays out over the course of the next few weeks," Hanke said.

Asked if this new secret, whatever it may be, was added to Pokemon Go in its new Halloween update, Hanke wouldn’t budge. "I am not giving you any clues," he said.

Pokemon Go’s Halloween update came out at the end of October, with its special content and features having wrapped up on November 1. More recently, Niantic updated Pokemon Go this week with a new daily catch bonus feature. Players quickly mined that update and discovered references to more than 100 new Pokemon, though it’s unclear if this is the secret that Hanke was alluding to.

In other Pokemon Go news, Niantic has kicked off a new limited-time promotion whereby players will find more Pokemon in the world, while PokeStops will have even more items available. This runs until November 11.

Pokemon Go is a major phenomenon. It’s been downloaded more than 500 million times and it brought in a reported $600 million in its first 90 days.