Google owner Alphabet has made an offer to acquire US wearable device maker Fitbit, as it eyes a slice of the crowded market for fitness trackers and smartwatches, people familiar with the matter said on Monday.

While Google has joined other major technology companies such as Apple and Samsung in developing smart phones, it has yet to develop any wearable offerings.

There is no certainty that the negotiations between Google and Fitbit will lead to any deal, the sources said, asking not to be identified because the matter is confidential. The exact price that Google has offered for Fitbit could not be learned.

Google and Fitbit declined to comment.

Fitbit shares were up 27.4 percent Monday afternoon, at $5.49.