US senators questioned Facebook CEO Mark Zuckerberg in a letter Wednesday about the social network's policies regarding hate speech and discriminatory targeting, as well as disinformation around the coronavirus pandemic and also the 2020 US presidential election.

"With federal, state, and local elections slated for November 2020, Facebook has a responsibility to ensure that its platforms do not become a hotbed of disinformation," says the letter, from Democratic Sens. Richard Blumenthal of Connecticut, Kamala Harris of California, and Robert Menendez of New Jersey.

While recognizing Facebook's recent steps to deal with COVID-19 misinformation, the senators said they're "deeply troubled" by the social media platform not addressing human and civil rights issues like hate speech and discriminatorily targeted advertising, and by the company's policy to leave up political candidates' ads that contain falsehoods. "These failings present real danger to people of color, especially with regard to protecting voting rights in the upcoming 2020 elections," they said.

The letter adds that Facebook has failed to prevent posts about fake cures and conspiracy theories during the COVID-19 pandemic.

Blumenthal, Harris and Menendez have asked Facebook whether it will reconsider, before the presidential election, its fact-checking policy regarding politicians' posts; whether it will permit factually inaccurate posts about COVID-19 and the election process by politicians; how Facebook is addressing hate speech, such as misinformation about Asian-Americans; how it reviews content that could lead to voter suppression; and whether it will add a civil and human rights expert to its board.

They expect answers from Facebook by May 22. Facebook said it plans to respond.