(AP) -- Former Secretary of State Hillary Rodham Clinton urged Congress on Tuesday to reauthorize federal legislation that compensates first responders who got sick working at ground zero in the aftermath of the Sept. 11 attacks, saying thousands still need help.

During a fundraising event in lower Manhattan, the former U.S. senator from New York and potential Democratic presidential candidate called on union members to mobilize to fight for the extension of the James Zadroga Act.

"It's absolutely crucial that we muster the same passion and pressure to extend the law that helped pass is it in the first place," said Clinton, who represented New York at the time of the attacks.

The James Zadroga 9/11 Health and Compensation Act provides medical treatment and compensation to those who got sick because of exposure to toxic air after Sept. 11. But its two components are set to expire in 2015 and 2016. Legislation that would reauthorize the act for 25 more years is set to be introduced in the House and Senate on Wednesday, a spokesman for one of the Senate sponsors, Kirsten Gillibrand, said Tuesday night.

Speaking to several hundred union members and advocates at the United Federation of Teachers headquarters, Clinton recalled visiting the rubble of the World Trade Center in the immediate aftermath of the attack and seeing the toxic air that rescue and recovery workers were breathing.

"It was just a scene out of 'Dante's Inferno.' It was as close to hell as I can imagine any of us experiencing," she said. "All you had to do was be there and you knew that there were going to be consequences to the people who had survived and the people who had conducted rescues and the people who were going to be there as long as it took to rebuild."

She said thousands had been helped by the law, but thousands still needed help.

"Last week with the anniversary, we mourned. This week we mobilize," she told the group.

As she was leaving the stage, several protesters with the youth immigrant group United We Dream burst into chants of "undocumented, unafraid," and were escorted out of the room by security.

Mateo Tabares, 19, of Queens, whose family came from Colombia, wanted to ask Clinton whether she would follow President Barack Obama's lead and continue to deport individuals who have entered the country illegally.

The event benefited the groups Health Watch Inc. and Citizens for the Extension of the James Zadroga Act.