Beckley, West Virginia (CNN) -- President Obama paid tribute Sunday to 29 workers killed in an explosion at a West Virginia coal mine earlier this month, saying they died "in pursuit of the American dream."
"All the hard work; all the hardship; all the time spent underground; it was all for their families. ... It was all in the hopes of something better," Obama said during a memorial service for the fallen miners in Beckley, West Virginia.
Obama and Vice President Biden, who were among a group of dignitaries who spoke at the service, met with the workers' families privately before the ceremony.
In his eulogy, delivered from behind a row of 29 white crosses, Obama sought to comfort those loved ones.
"We have been mourning with you throughout these difficult days," he said. "Our hearts have been aching with you."
Biden offered similar words of comfort, saying the fallen miners "represent, what I believe is the heart and soul and spine of this nation," and adding "a nation mourns them."
The April 5 blast at the Upper Big Branch Mine was the worst U.S. mine disaster in nearly 40 years.
Obama ordered a review earlier this month and blamed mine officials for lax regulation and lack of oversight.
On Sunday, he said: "We cannot bring back the 29 men we lost. ... Our task ... is to save lives from being lost in another such tragedy. To do what must be done, individually and collectively, to assure safe conditions underground."
West Virginia Gov. Joe Manchin, who was a constant presence during the recovery efforts at the mine, also spoke at the service, telling the crowd of mourners that it was the day "to begin the healing process."
Manchin said each of the 29 men, like their fathers and grandfathers, had not only a strong commitment to their work, but also "a deep, patriotic pride that the work they did and the energy they produced made America strong and free."
He called on Americans to "say a prayer for every coal miner working today," and to "not only thank them -- but to honor them for their work and their patriotism."
He also made a vow: "After today, we turn our focus on their legacy," he said. "I don't have the answers about why this has happened, but I promise you we will find the answers."
Sen. Jay Rockefeller, D-West Virginia, echoed that vow during his remarks at the service, saying: "We will pass legislation to meet the requirements of those answers. And we will do it for you, the miners of West Virginia and America."
"West Virginia, all of West Virginia, is in pain, and not without some anger," Rockefeller added. "But we will find our solace and bind together as a community because that is what West Virginians do."
The somber service began with Manchin accompanying families as they lay helmets on top of 29 crosses.
A photo of each of the men killed in the disaster was displayed on large screens, and the crowd applauded for each one.
The service closed on a stirring note, as one by one, each of the headlamps on the symbolic helmets were lighted while a chorus sang "This Light of Mine."