The office of the Manhattan district attorney, Cyrus R. Vance Jr., convened what is known as an investigatory grand jury to examine the accusations.

In the course of the investigation, prosecutors created what amounted to an elaborate timeline of Mr. Weinstein’s whereabouts in an effort to take advantage of a section of New York State law that says the clock stops ticking toward the statute of limitations when a defendant is continuously outside the state. Investigators compiled instances in which Mr. Weinstein left New York to determine whether some accusations of assault, even if they appeared to fall outside the statute of limitations, could in fact be included in criminal charges.

The federal investigation of Mr. Weinstein, which began last year, focused on fraud allegations in connection with two auction items that were to be offered together at an AIDS charity fund-raiser in France in May 2015, the people have said. The items were a sitting with a famous fashion photographer and a package of tickets to a Hollywood awards event and party. That investigation expanded into a review of whether Mr. Weinstein violated federal stalking laws, the people said.

News outlets have reported on dozens of allegations against Mr. Weinstein, many of them sharing a common narrative: Women reported to a hotel for what they thought were work reasons, only to discover that Mr. Weinstein sometimes seemed to have different interests.

But it remains to be seen how sweeping the charges against Mr. Weinstein will be, and how much supporting evidence prosecutors will be allowed to introduce in seeking to show a pattern of criminal behavior.

That is one of many hurdles sex crime prosecutions often face, ever more so in cases of powerful men like Mr. Weinstein who come armed with high-priced lawyers and private investigators.

New York Police Department officials said as early as November that detectives were gathering evidence with an eye toward preparing a warrant to arrest Mr. Weinstein. But as Mr. Vance’s investigation continued, the pace of prosecutors’ work fueled tensions between the police and district attorney’s office.

Mr. Vance’s office faced added pressure because it decided not to prosecute Mr. Weinstein after Ms. Battilana accused him of groping her in 2015. Mr. Vance said the evidence was not strong enough to win a conviction and dropped the investigation, despite having an audiotape of Mr. Weinstein acknowledging he had touched her breasts and promising not to do so again. The decision by prosecutors followed lobbying by Mr. Weinstein’s lawyers, who pointed to shifting accounts by Ms. Battilana in sworn testimony in another sexual assault case in Italy.

In recent months, Mr. Vance has been under tremendous pressure from activists and elected leaders to resolve his office’s investigation into Mr. Weinstein. Gov. Andrew M. Cuomo ordered a review of his handling of the 2015 allegations and women’s advocates have criticized the slow pace of Mr. Vance’s investigation.