Yelp Inc. is exploring a sale as the company at the top of many Internet search results struggles to post strong growth with users and advertisers.

The San Francisco-based site was willing five years ago to go it alone despite an acquisition offer from Google Inc. Today, it is working with investment bankers and sounding out potential buyers, people familiar with the matter said.

A deal isn’t imminent, one of the people cautioned, and may not happen at all.

But that willingness itself is a sign of the struggles at a company that has amassed millions of consumer reviews of everything from restaurants to dentists to hair salons.

Yelp is contending with a host of troubles: slowing user growth, rising costs, a return to a quarterly loss and a stock price that has shed more than half its value since its high last year.