(Bloomberg) -- The US Federal Trade Commission is preparing a possible lawsuit against Amazon.com Inc. that could be filed as soon as this spring, according to people familiar with the investigations.

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The allegations the agency is preparing to make and the timeline for filing a complaint are still in flux, said the people, who asked not to be named speaking about a confidential probe.

The agency, which has both antitrust and consumer protection mandates, has been investigating Amazon for several years. A probe into the e-commerce giant’s retail business, which started in 2019 under the Trump administration, later expanded into recent acquisitions, such as the $8.45 billion MGM studio deal, and cancellation policies related to Amazon’s Prime service.

The company also has two deals under antitrust review at the agency: a $3.5 billion acquisition of One Medical parent 1Life Healthcare Inc. and the $1.65 billion deal to buy Roomba vacuum maker iRobot Corp.

Those deals could potentially be included in an FTC antitrust complaint, the people said.

California sued Amazon last fall, saying the company forces third-party merchants to agree to policies that lead to “artificially high prices” for consumers. That case, filed in California state court, accuses Amazon of punishing merchants that offer lower prices on other websites. The lawsuit is ongoing and could take years to resolve. The California attorney general’s office and the FTC have been in contact on their respective probes, the people said.

Small merchants on Amazon’s retail marketplace have complained for years about what they see as a one-sided relationship, accusing the company of arbitrarily enforcing its rules and being slow to respond when something goes wrong. Merchants have said Amazon punishes them by burying their products on its webstore when they offer lower prices elsewhere, such as on Walmart.com.