Federal authorities are expected to arrest Sheldon Silver, the powerful speaker of the New York State Assembly, on corruption charges on Thursday, people with knowledge of the matter said. The case is likely to throw Albany into disarray at the beginning of a new session.

The investigation that led to the expected charges against Mr. Silver, a Democrat from the Lower East Side of Manhattan who has served as speaker for more than two decades, began after Gov. Andrew M. Cuomo in March abruptly shut down an anticorruption commission he had created in 2013.

Details of the specific charges to be brought against Mr. Silver were unclear on Wednesday night, but one of the people with knowledge of the matter said they stemmed from payments that Mr. Silver received from a small law firm that specializes in seeking reductions of New York City real estate taxes. The total amount of the payments was unclear, but another person has said they were substantial and were made over several years.