The raucous debate over the Atlantic Yards development spilled out into the streets yesterday as an overcrowded public hearing left hundreds of Brooklynites arguing with each other over the mega-project’s merits.

The public hearing was a necessary step toward securing final approval of the $4.2 billion plan to build a basketball arena and 16 towers containing 6,860 apartments on 22 acres near downtown Brooklyn. Some of the development would be built over the Atlantic rail yards, and some on land bought by the developer or to be seized using eminent domain.

Opponents, mainly white, have complained that the project, which will create the densest census tract in the country, will negatively impact the community’s infrastructure, ensnarl traffic, and ruin its low-rise character. Supporters, who appear to be predominantly African American, say that it will bring about 2,250 units of “affordable” housing to a borough facing soaring housing costs, and bring much needed jobs.

The 800-seat auditorium of New York City Technical College was at capacity and hundreds of people waited outside on a line that bent around the corner, where many engaged in charged, informal debates over the project.

Inside the auditorium, more than 250 people signed up to speak. With each speaker allotted three minutes, the state’s moderator, Ted Kramer, said there could be more than 12 hours of public testimony.

Despite a warning from Mr. Kramer that “cheering, booing, and placard waving” was not allowed during public testimony, a lively, diverse crowd colorfully interrupted speakers at will. One local resident against the project, Connie Leshold, 68, was removed from the auditorium by security after to she stood up, yelling and pointing at state Senator Martin Golden.

Just before the public hearing began, developer Bruce Ratner held a celebrity-filled press conference nearby. “This is about affordable housing, jobs, and bringing a spirit back to Brooklyn,” Mr. Ratner said.

The developer owns the New Jersey Nets, and hopes to move them to the Atlantic Yards arena. Nets stars Jason Kidd and Vince Carter were on hand at the press conference yesterday, along with singer Roberta Flack.

Opponents at a recent rally brought out celebrities like Steve Buscemi and Rosie Perez, but a spokesman for the umbrella group against Atlantic Yards, Develop Don’t Destroy Brooklyn, Daniel Goldstein, said that no celebrities were on hand yesterday.

Inside the auditorium, debate continued in the aisles and in the foyer. A student from Boston College and Brooklyn native, Benjamin Lee, said he favors the project because it would revitalize the borough. “The rail yards are just a big, unused space,” Mr. Lee said.

Yesterday’s hearing also represented the only time that property owners in the project’s footprint can go on the public record to oppose the state’s pending property condemnation.

An attorney who lives in the footprint, who requested anonymity, said he had discussed with the developer the idea of selling his home, which has been in his family for three generations.

“We’ve talked but I find the idea of selling out offensive,” he said. “It will create a lot of affordable housing, but in doing so it will kick out my grandfather, who could afford this housing 30 years ago.”

On September 12, the state will hold a community forum about the project. The state’s development agency will review the public comments over the next 30 days and incorporate changes into the general project plan and final environmental impact statement, which must be approved by the agency’s board and the Public Authorities Control Board. The developer hopes to open the basketball arena for the 2009 season.