Federal prosecutors in Manhattan investigating possible financial improprieties by the disgraced movie mogul Harvey Weinstein have broadened their inquiry to include allegations that he may have violated federal stalking laws, several people with knowledge of the matter said on Wednesday.

The expansion of the inquiry, first reported by The Wall Street Journal, added to the legal risks facing Mr. Weinstein. For several months, local prosecutors in Manhattan and Los Angeles, and the police in London, have been investigating accusations that he sexually assaulted numerous women; none of those investigations have led to criminal charges. Mr. Weinstein has also been accused in several civil lawsuits of sexual and physical assault and of waging smear campaigns against his accusers.

The federal investigation started late last year when prosecutors from the United States attorney’s office in Manhattan began to examine whether Mr. Weinstein had committed fraud when he arranged for two auction items — a sitting with a famous fashion photographer and a package of tickets to a Hollywood awards event and party — to be offered together at an AIDS charity fund-raiser in France in May 2015. There was one condition to the deal, said people with knowledge of the matter: $600,000 of the proceeds had to go to a theater staging a Broadway musical that Mr. Weinstein was producing.

According to the people familiar with the case, that investigation, which is being handled by the Complex Frauds and Cybercrime Unit of the Manhattan federal prosecutors’ office, quickly expanded to include the possibility that Mr. Weinstein broke federal stalking laws in his dealings with women who have accused him of sexual assault. Those laws forbid crossing state lines to kill, injure, harass or intimidate victims.