Federal prosecutors are expected to announce criminal charges against New York state Senate Majority Leader Dean Skelos imminently, possibly as soon as Monday, in connection with a continuing corruption investigation, according to a person familiar with the matter.

The U.S. attorney’s office in Manhattan and the Federal Bureau of Investigation in New York have been investigating Mr. Skelos and his son, Adam, as part of a wider probe into allegations of corruption in Albany. Both men are named in a lengthy criminal complaint being prepared by prosecutors that as of this week included allegations of conspiracy, extortion and solicitation of bribes, according to the person.

The activity detailed in the draft complaint involves a real-estate developer and an environmental technology company, according to the person.

The Skelos inquiry, which includes information presented to a grand jury, had been looking, in part, at the business dealings of the younger Mr. Skelos and whether his father, one of the most powerful Republicans in the state, did anything improper to help him, according to people familiar with the matter.

A spokesman for Mr. Skelos, 67 years old, didn’t immediately respond to a request for comment. Mr. Skelos said last month that he has “and will continue to cooperate with any inquiry.”

An attorney for Adam Skelos didn’t immediately respond to a request for comment.