Several of Facebook’s top advertisers have remained silent as a growing number of companies continue joining a temporary boycott of ads on the service. The boycott is part of an effort to denounce the social media giant’s handling of hate speech.

Top advertisers on Facebook this year include Disney, Procter & Gamble, the U.S. Census Bureau, Home Depot, CBS, Wix.com, Purple Innovation, Domino’s Pizza, Sprint, and Walmart, according to data from digital marketing firm Pathmatics. None of those companies have joined the #StopHateForProfit campaign, which calls for companies to pause advertising on Facebook during the month of July.

Home Depot and P&G were the only two advertisers of the group to comment on the matter in response to requests from Fortune.

Home Depot issued a statement after Facebook’s Friday announcement that the service planned to crack down on hateful messaging in ads and posts from politicians. “Given the measures [Facebook] just announced, we’re watching this very closely,” said spokeswoman Sara Gorman. “Like others, we’re disgusted by hate speech and discriminatory content we see on social media.”

P&G pointed to comments its chief brand officer Marc Pritchard made during the digital forum Cannes Lions Live on June 24. During the forum, Pritchard said the company was in the process of reviewing every platform it advertises on to ensure “that we are not advertising on or near content we determine to be hateful, discriminatory, denigrating, or derogatory.” He continued: “As part of that, we’re working with media companies and platforms to take appropriate systemic action where needed.”

The top advertisers have collectively spent more than $550 million on Facebook ads this year, according to Pathmatics. Several of them were also some of the top advertisers last year, with Home Depot and Walmart spending the most money. Home Depot spent $179 million in ads last year, while Walmart spent $147 million.

Last week, big brands including Verizon, Unilever, Honda, and Hershey’s joined the boycott created by organizations including the Anti-Defamation League, the National Association for the Advancement of Colored People, and Common Sense. The campaign aims to pressure Facebook into taking more action to stop hate from spreading on its service.

The boycott has garnered the support of more than 180 companies, many of which are small- and medium-size businesses, since it started. But as the campaign began to gain steam late last week with participation from big brands, Facebook’s stock started to drop. The stock has declined about 8% in the past week, trading at $220 per share on Monday.