White House Press Secretary Josh Earnest said Tuesday that the U.S. airstrike on an Afghanistan hospital where aid workers were operating was a "profound tragedy" and President Obama wants a "full accounting of what transpired" -- but clarified that the Justice Department is not involved in any investigation after earlier saying it was. 

"I misspoke," Earnest said. 

Earnest initially said during Tuesday's press briefing that the Justice Department was conducting an investigation. 

Later in the briefing, Earnest corrected himself, saying there are still only the three probes announced in the aftermath of the attack, to be conducted by: the Defense Department, NATO, and a joint U.S.-Afghan group. 

The weekend strike in Kunduz killed at least 22 at a medical clinic run by Doctors Without Borders. U.S. officials say Afghan forces called in the strike after taking fire from Taliban fighters. 

Earnest said Tuesday "there still is more that needs to be learned" about how the attack happened.

Shortly beforehand, Gen. John F. Campbell told the Senate Armed Services Committee on Capitol Hill that the attack was a mistake. 

"The hospital was mistakenly struck," he said. "We would never intentionally target a protected medical facility."

Campbell, the top commander of American and coalition forces in Afghanistan, also said the decision to execute the airstrike in Kunduz was made by top U.S. commanders. He said Monday that Afghan forces, not U.S. forces, called in the strike after taking fire. 

Campbell’s characterization that the airstrike was an accident comes after sources told Fox News that Taliban fighters were inside the Doctors Without Borders-run hospital. Campbell said he could not provide more details about what happened, including who may have failed to follow procedures for avoiding attacks on hospitals. He said he must await the outcome of multiple investigations. 

Campbell, speaking more generally about difficulties in the country, also said Afghan forces have "faltered" in efforts to battle Al Qaeda, the Taliban and other extremist groups. But while acknowledging difficulties with the Afghan allied forces, Campbell also praised their efforts.

“The [forces] have rendered a creditable, overall performance for a young force that has been severely tested” and have “taken ownership of the fight,” the general said.

He also said American efforts have been welcomed by the Afghan government and citizens, unlike in Iraq.

Campbell repeatedly deflected committee members’ questions about how many of the 9,800 American troops in Afghanistan should withdraw and when.

He said he has been “asked to provide course of action” and “options based on the last two years.”

However, he suggested that a purported plan by President Obama to reduce the U.S. troop presence of 9,800 to an embassy-based security operation of about 1,000 in Kabul was not the best idea toward providing additional training and security.

“Our ability … would be limited,” Campbell said.

He said Afghanistan “remains a very dangerous place” but suggested extremists groups will not overthrow the Afghan government by force.  

The president is also considering keeping as many as 5,000 troops through 2016, a senior defense official told Fox News. 

Before the hearing, Sen. Tom Cotton, R-Ark., a member of the Armed Services panel, called for having as many as 10,000 U.S. troops.

Defense Secretary Ash Carter said Monday the Pentagon is providing options to the White House, and Obama will be making decisions about future force levels later this fall.

Campbell's testimony comes three days after the airstrike on the medical clinic in the northern city of Kunduz.

Kunduz has been the scene of heavy fighting in recent days.

A Taliban assault on Kunduz took Afghan authorities by surprise and embarrassed President Ashraf Ghani's administration. The Taliban, who attacked on multiple fronts, held the city for three days before a government counter-offensive began. Afghan forces have retaken Kunduz, an important city on the Tajikistan border, a hub for drug and gun smuggling to and from Central Asian countries.

Fox News' Lucas Tomlinson and The Associated Press contributed to this report.