Facebook Inc has been ordered by a Massachusetts judge to turn over material to the state's attorney general about thousands of apps that the social media company suspected may have misused customer data.

In a decision made public on Friday, Massachusetts Superior Court Justice Brian Davis said Attorney General Maura Healey had demonstrated a "substantial need" for the material, as she investigates Facebook's privacy practices.

US President Donald Trump gestures at his office in Washington. File photo

Healey began her probe in March 2018, following news that Facebook had let British political consulting firm Cambridge Analytica access data for as many as 87 million users.

Cambridge's clients had included US President Donald Trump's 2016 election campaign.

Davis said Facebook did not show that most of the material Healey sought, including the identities of developers behind suspect apps, was protected by attorney-client privilege or an attorney "work product" that did not need to be disclosed.

"Only Facebook knows the identity of these apps and developers, and there is no other way for the attorney general to obtain this information on her own," Davis wrote.

Facebook said it was reviewing its options and may appeal.

"We are disappointed that the Massachusetts Attorney General and the court didn't fully consider our arguments on well-established law, including the work product doctrine," it said.

According to court papers, the Menlo Park, California-based company's own probe led it to suspend 69,000 apps last September, mostly because their developers did not cooperate.

Reuters