State attorneys general investigating whether Google is engaged in monopolistic behaviour are planning to take a deep look into the tech giant’s advertising business. The office of Texas Attorney General Ken Paxton sent a letter to Google on Monday seeking internal documents about how it sells ads and tracks the behaviour of people who use its search engine and other products.

The letter was sent on the same day Paxton and other state prosecutors announced the multistate antitrust probe. The Texas-led investigation involves 48 states along with Puerto Rico and the District of Columbia.

Paxton’s document request seeks more information about how Google acquired and integrated advertising platforms such as DoubleClick and AdMob. It also seeks information about the advertising practices of Google’s Chrome browser and its YouTube video service.

Earlier, fifty US states and territories, led by Texas, had announced an investigation into Google’s “potential monopolistic behaviour.”

Nebraska attorney general Doug Peterson, a Republican, said at a press conference held in Washington that 50 attorneys general joining together sends a “strong message to Google.”

California and Alabama are not part of the investigation, although it does include the District of Columbia and Puerto Rico. Google is headquartered in California and employs more workers there than in any other region. Google also broke ground last year on a $600 million (roughly Rs. 4,300 crores) data-centre project in Alabama.

Tara Gallegos, a spokeswoman for California Attorney General Xavier Becerra, declined to confirm or deny any state investigation and would not comment on the announcement by the other states. Mike Lewis, a spokesman for Alabama Attorney General Steve Marshall, also said the state’s legal team had no comment on the probe.