SAN FRANCISCO (AP) — YouTube's inability to keep big-brand ads off unsavory videos is threatening to transform a rising star in Google's digital family into a problem child.

It's not yet clear whether a recent ad boycott of YouTube will be short-lived or the start of a long-term shift away from the video service that could undercut Google's growth, and that of its corporate parent, Alphabet Inc.

Alphabet's first-quarter results released Thursday provided few clues, as major advertisers didn't start pulling back from YouTube until the period was nearly over. The company's earnings rose 29 percent to $5.4 billion while revenue climbed 22 percent to $24.8 billion.

But the fallout from the YouTube boycott is likely to be felt in future quarters as skittish advertisers curtail their spending on the world's biggest video site.