President Joe Biden announced Thursday that he is commuting the sentences of some 1,500 individuals and pardoning 39 people convicted of non-violent crimes – marking a broad use of the presidential clemency power just weeks from the end of Biden’s administration.

White House officials are billing Thursday’s move as the biggest single-day act of clemency in modern history. The president, who has come under growing pressure to grant more clemencies before he leaves office and who controversially granted a pardon to his son Hunter earlier this month, also promised that additional action will be announced in the weeks to come.

“America was built on the promise of possibility and second chances,” Biden said in a statement released shortly after CNN reported early Thursday morning on the coming announcement. “As President, I have the great privilege of extending mercy to people who have demonstrated remorse and rehabilitation, restoring opportunity for Americans to participate in daily life and contribute to their communities, and taking steps to remove sentencing disparities for non-violent offenders, especially those convicted of drug offenses.”

The nearly 1,500 individuals whose long sentences are being commuted Thursday were placed on home confinement during the Covid-19 pandemic, and were deemed to have demonstrated a clear commitment to rehabilitation and reintegration into their communities, sources said. The 39 people being pardoned were convicted of non-violent crimes, and considered to have demonstrated records of meaningfully giving back to the country.

“They are individuals who have secured employment, advanced their education, served as caretakers for their children and family members, and have really reintegrated into the tapestry of their communities,” an administration official familiar with the announcement told CNN. “They include individuals who faced incredible challenges in life and have really now shown resilience and seeking to overcome those challenges.”

While CNN has not obtained a full list of names of the clemency recipients, sources provided several examples of individuals being pardoned.

Among them: A decorated military veteran described as having devoted much of his time helping members of his community including the sick and elderly; a nurse who is said to have helped during natural disasters and was at the forefront of vaccination efforts during the Covid-19 pandemic; as well as an addiction counselor recognized for his dedication to mentoring young men of color.

Thursday’s announcement is expected to be widely celebrated by human rights activities, advocacy groups, Democratic lawmakers and the families of those receiving the commutations and pardons.

As the president’s first term approaches its end, calls for Biden to more aggressively and widely exercise his clemency power before incoming president Donald Trump takes office have only grown louder – including by taking several dozen inmates off of federal death row. (Biden has publicly opposed capital punishment.)

Biden has previously pardoned military veterans convicted of having gay sex – formerly a crime under military law – and also issued pardons to those convicted of marijuana possession.

The historic announcement came after intense advocacy from criminal justice and civil rights groups. Their contacts with the White House picked up before November, “to figure out what a post-election clemency effort might look like,” according to a senior official from a pro-clemency group that has been lobbying the Biden administration.

These meetings often involved the White House Counsel’s office and the Domestic Policy Council. White House staffers were “receptive” to this outreach, which largely came from liberal-leaning groups that have aligned with the administration, but staffers didn’t tip their hand about how far the president was planning to go, the official said.

Biden’s announcement broke some previous records set by former President Barack Obama, who issued a spate of pardons and commutations before leaving office in 2017.

But some still want more from Biden. The official from the advocacy group said they were “pleasantly surprised” by Biden’s latest commutations – but noted that this latest round of clemency won’t actually free all that many people from living behind bars.

“These people were already home,” the official said, referring to the 1,500 people who got commutations Wednesday, who were already on house arrest after being released from prison amid the Covid-19 pandemic. “We are hoping for more commutations that will actually bring people home from prison, and shorten some very lengthy sentences.”

Thursday’s news comes on the heels of Biden’s decision to issue a full and unconditional pardon of his son Hunter after repeatedly insisting over the course of several months that he would not do so. The move sparked an uproar, including among some of the president’s allies and fellow Democrats who questioned his decision to renege on his word.

Anita Dunn, a former senior adviser to the president, said last week that the move struck her as “exceptionally poor timing.”

Biden’s pardoning of his son, the administration official insisted, has not shaped his thinking on the use of his clemency power overall.

“The President has shown his views on clemency and how he can use the clemency power to make our country more equitable, more just, repair some of the past wrongdoings that we’ve seen in the criminal justice system, and that continues to be how the president is viewing the petitions that he is and will be reviewing over the coming weeks,” they said.

With less than six weeks left until the end of Biden’s term, the president is expected to provide further relief.

“I will take more steps in the weeks ahead,” Biden said. “My Administration will continue reviewing clemency petitions to advance equal justice under the law, promote public safety, support rehabilitation and reentry, and provide meaningful second chances.”

The president has been consulting with White House Counsel Ed Siskel and the lawyers at the counsel’s office about a range of clemency options, sources said. The White House counsel’s office has also been in consultation with the Justice Department’s Office of the Pardon Attorney.

CNN’s Marshall Cohen contributed to this story.