The group of 50 attorneys general investigating Google's market dominance will also probe the company's search and Android businesses, expanding their investigation, according to CNBC.

When Texas Attorney General Ken Paxton first announced the investigation — launched alongside nearly every state attorney general in the country — he said the focus was Google's online advertising business. But as it has progressed, according to CNBC, the attorneys general have decided some states will also look into Google search and Android, the company's mobile operating system.

The states will soon issue civil investigative demands (CIDs) — a kind of subpoena — to obtain documents for the expanded probe, sources familiar with the matter told CNBC. They have already requested documents about Google's ad business.

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After the investigation was first announced earlier this year, Paxton said in a statement, "At this point, the multistate investigation is focused solely on online advertising; however, as always, the facts we discover as the investigation progresses will determine where the investigation ultimately leads."

Google has said it will comply with all government antitrust investigations. The tech giant denies all allegations that it functions as a monopoly, insisting in a September blog post, "Google's services help people, create more choice, and support thousands of jobs and small businesses across the United States."

In September, the group of attorneys general announced they will investigate Google for potential violations of antitrust law, a step that could lead to a broad legal challenge to the company’s market dominance.

"This is a company that dominates all aspects of advertising on the internet and searching on the internet as they dominate the buyers' side, the sellers' side, the auction side and even the video side with YouTube," Paxton said while announcing the investigation at a press conference on the steps of the Supreme Court.

The company is also facing an antitrust investigation from the Department of Justice, which recently requested documents from Google, and investigators in the House.

Nearly 90 percent of web searches go through Google or its subsidiary YouTube.

In 2018, European Union regulators fined Google $5 billion for violating antitrust laws by pre-installing its own products, like Google Chrome, on Android devices.