Homeland Security Secretary Jeh Johnson vowed Friday to “transform and reform” the Secret Service in the wake of high-profile security failures that led this week to the resignation of the agency’s director, telling Fox News that an independent board will soon be asking the “hard questions.”

In an interview on “Special Report with Bret Baier,” Johnson said he plans to name members of that board “in the next couple of days.”  

He declined to offer details about “who knew what, when” regarding recent security incidents but said: “I’m more focused on what we need to do to ask the hard questions.”

Johnson earlier this week accepted the resignation of director Julia Pierson -- not two weeks after a Sept. 19 security breach in which an intruder jumped over the White House fence and darted past several agents before making it all the way into the East Room.

It was also revealed that on Sept. 16, a security guard with an arrest record and a gun got into an elevator with President Obama in Atlanta, violating agency protocol. Retired agent Joseph Clancy, who once served on Obama’s security detail, has since stepped in as interim director following Pierson’s resignation.

“I’m focused on what we need to do to rebuild the trust and confidence,” Johnson told Fox News.

Johnson, though, pushed back when questioned on whether the Secret Service should come out from under the auspices of DHS. The agency used to be under the Department of the Treasury, but was put under DHS when the umbrella agency was created in 2004. 

The Fox News interview covered a range of topics, including reports last month that four men with suspected Middle East terror ties had been apprehended at the southern border in Texas and detained. The incident had been raised by Rep. Jason Chaffetz, R-Utah, who sits on the House Homeland Security Committee.

Johnson acknowledged Friday that the men were indeed taken into custody and they “have been scrutinized very, very carefully.” At this point, he said, there is “no evidence that these individuals were tied to terrorism.” They remain in custody, however, due to documentation issues. He provided no additional details.

On the so-called Khorasan Group in Syria, which officials in the administration have said is actively plotting attacks against the U.S. and which was targeted by U.S. airstrikes, Johnson addressed recent questions about whether the threat might have been overblown.

“They are a terrorist organization that has the potential to threaten our interests here at home, which is why we took action,” he said, describing them as a “very real concern.”

He would not say whether the group is the same as “core Al Qaeda,” though other U.S. officials have suggested they are closely tied. Notably, he did not repeat the administration claim that core Al Qaeda has been “decimated,” saying only that the U.S. has “come a long way” in targeting the group’s leadership.

On the developing Ebola crisis, Johnson also stressed that the government is not pushing for blocking flights in or out of the West African countries now trying to contain an outbreak of the virus, as some have called for.

More than 3,000 people have died of the virus and a handful of Americans have been flown to the U.S. for treatment. A man who traveled from his home in Liberia is currently being quarantined and treated for Ebola in Dallas after being diagnosed in the U.S. Five members of his family are being quarantined and under observation for symptoms.

“We’re doing a lot to deliver health care to these affected countries,” Johnson said. “Shutting down the ability to travel entirely is not the way to go in our judgment.” He said among other measures, they are screening people on flights, particularly passengers coming in from the affected countries through Chicago, New York and Washington, the key points of entry in the U.S.