Democratic presidential nominee Hillary Clinton climbs into a vehicle outside the apartment of her daughter, Chelsea Clinton, in New York on Sept. 11 after she left a 9/11 ceremony because she felt “overheated.” (Brian Snyder/Reuters)

Hillary Clinton’s campaign will release additional medical records this week, a campaign aide said, bowing to growing criticism about how the campaign handled news of her pneumonia diagnosis.

“We’re going to be releasing additional medical information,” Clinton spokesman Brian Fallon said on MSNBC on Monday. “We’re going to be releasing that to further put to rest any lingering concerns about what we saw yesterday.”

The decision to make additional disclosures came as the campaign has come under a new round of scrutiny for a lack of transparency following Clinton’s abrupt, stumbling departure from a commemoration Sunday of the 15th anniversary of the Sept. 11, 2001, terrorist attacks. Democrats and Republicans alike criticized Clinton for leaving the public and the media in the dark for much of the day, feeding rumors about Clinton’s health and fueling the perception that she is unnecessarily secretive.

Aides acknowledged Monday that the campaign should have handled news of Clinton’s dizzy spell and pneumonia diagnosis differently.

“We could have done better yesterday, but it is a fact that the public knows more about HRC than any nominee in history,” wrote Clinton communications director Jennifer Palmieri on Twitter in response to the criticism, using the initials of the Democratic presidential nominee.

The Fix's Aaron Blake explains the incident during which Democratic presidential nominee Hillary Clinton fell ill on Sept. 11, and why her health is likely to remain a subject of discussion. (Peter Stevenson/The Washington Post)

At the memorial service Sunday morning, Clinton became overheated and dehydrated, according to the campaign. Video footage showed her buckling as she was helped into a waiting van by her security detail.

Throughout the day on Sunday, however, the campaign said little. Clinton left the event early, leaving her small group of traveling reporters behind at several points in the day. More than an hour and a half passed between Clinton’s departure and the campaign’s decision to inform traveling reporters of her whereabouts.

Long after the campaign finally revealed Clinton’s pneumonia diagnosis, aides announced she would cancel a planned trip to California on Monday and Tuesday.

Clinton expects to return to the campaign trail later this week and has no other unrevealed illness, Fallon said.

On CNN later Monday, Fallon said that senior campaign staff was told of the pneumonia diagnosis on Friday, but he dodged a direct answer on whether voters deserved to have known that day as well.

The illness spoiled a planned pivot for Clinton this week to present some of her policy plans in a more personal fashion. In addition to two planned policy speeches that Palmieri had said would draw on Clinton’s background and biography, this week marked the start of intensive campaigning by the biggest names Clinton has in her corner, including President Obama and first lady Michelle Obama.

The heavy hitters are part of a Clinton campaign effort to focus voter attention on Clinton in her own right, and to try to steal some of Trump’s thunder. Palmieri told reporters last week that the campaign had sometimes found it hard to be heard over Trump.

Donald Trump responded to Hillary Clinton's recent diagnosis of Pneumonia on Monday, Sept. 12, saying he hopes she "gets well" and he plans to release "very, very specific" details about his own health soon. (Jenny Starrs,Bastien Inzaurralde/The Washington Post)

“This is an unusual election cycle and there is a great deal of interest in Donald Trump,” Palmieri said Thursday, as reporters flew to Kansas City, site of the first of at least three planned policy speeches meant to set markers for the election eight weeks away.

The second was to have been Tuesday in California.

Clinton will not appear in person at several fundraising events in California planned for Monday and Tuesday. She will instead remain at her home in Chappaqua, N.Y., to rest but will teleconference into a San Francisco fundraiser Monday night.

On Monday morning, Obama’s former campaign strategist, David Axelrod, gave voice to Democrats’ concerns that the campaign had prized secrecy over transparency, further playing into a perception among voters that Clinton is untrustworthy.

“Antibiotics can take care of pneumonia,” Axelrod wrote. “What’s the cure for an unhealthy penchant for privacy that repeatedly creates unnecessary problems?”

Former Pennsylvania governor Ed Rendell said that the campaign deserves credit for eventually revealing her diagnosis, but given the controversy that resulted from Clinton’s dehydration episode on Sunday, they might have been better off doing it sooner.

“They probably should have initially acknowledged her initial diagnosis,” Rendell said. “But because Trump and [Former New York Mayor Rudy] Giuliani had raised the issue of her health so brutally and so unfairly, they were inclined to try to gut it out and not disclose.”

Fallon noted in the MSNBC interview that Clinton was “dead-set” on attending the memorial service — and kept to her full schedule on Friday, the day of the diagnosis. But he, too, acknowledged that more information should have been forthcoming.

He explained that Clinton was “alert the whole time” after she was assisted into her motorcade van at Ground Zero, where she left abruptly after overheating and getting “a bit dizzy.”

“In those 90 minutes that elapsed, we could have gotten more information out more quickly,” he said.

Clinton had been diagnosed with pneumonia two days earlier, although the campaign did not mention it until late Sunday, in a statement from her doctor, Lisa Bardack, who said she had advised Clinton to rest and modify her schedule.

That same day, Clinton held a meeting with a bipartisan group of national security figures and addressed the media afterward, all by holding back a persistent cough. Later that night, Clinton appeared at an LGBT fundraiser in Manhattan with Barbara Streisand. It was at that event where Clinton made her controversial remark that half of Republican Donald Trump’s supporters are in a “basket of deplorables.”

Jim Manley, a Democratic operative who was a longtime aide to Democratic Senate Leader Harry M. Reid (Nev.), said that it was troubling, though not surprising, that so much time elapsed between Clinton’s departure from the event and an explanation as to what had happened.

“As someone who has watched them operate for years, none of this comes as a surprise,” Manley said. “They certainly could have been more open than they were. It fits a pattern that enemies are going to use against them.”

Former Vermont governor Howard Dean, who is a doctor, said he was “dismayed” by the media coverage of her illness, noting that Clinton’s failure to disclose her pneumonia paled in comparison to Trump’s lack of transparency.

But he urged the campaign to pare back the candidate’s schedule.

“Hillary need not to be working 25-hour days, which is what she’s been doing — and she can do that easily,” Dean said.

Meanwhile, Trump’s campaign manager, Kellyanne Conway, raised questions about Clinton’s handling of the situation.

“Lack of transparency is an overarching theme,” Conway wrote Monday morning, in response to a news story about the health episode.

But Palmieri noted, in response to Axelrod’s criticism, that Clinton has released more medical and financial information than Trump, who has refused to release his tax returns and released a letter from a doctor that was widely criticized for lacking any concrete medical information about his health.

“In contrast to HRC, Trump has been less transparent than any nominee in modern history,” Palmieri wrote.

Clinton’s doctor did release a letter detailing some aspects of her health, but she has not released as much medical information as some prior presidential candidates, including Arizona Sen. John McCain, who in 2008 released more than a thousand pages of medical records to be scrutinized by the media.

Perhaps anticipating this line of criticism, Trump said in a television interview Monday morning that he would release more “very, very specific” medical information soon.

“Hopefully they’re going to be good. I think they’re going to be good,” Trump said on Fox News on Monday morning. “I feel great.”

Gearan reported from Washington. John Wagner in Richmond, Va., contributed to this report.