The U.S. delayed by almost a month an effort to rescue American and British hostages of the Islamic State group in Syria last year, even though U.K. intelligence sources identified possible locations where they were being held, according to the Daily Beast. The Obama administration was unwilling to launch a rescue mission based on the foreign intelligence until it was too late, American and British officials told the media outlet.

The subsequently slain Americans included aid worker Kayla Mueller and journalists James Foley and Steven Sotloff.

U.K. authorities advised their U.S. counterparts in May about possible sites in the vicinity of Raqqa, the Islamic State group’s de facto capital in Syria, where the militant group had moved its captives, the Daily Beast reported. British intelligence agencies positively identified the hostages’ location in June and shared the information with the White House. However, U.S. President Barack Obama’s senior national-security advisers reportedly declined to act on it for nearly a month.

“The issue was that they didn’t trust it, and they wanted to develop and mature the intelligence, because it wasn’t our own,” a U.S. official, who requested anonymity, told the Daily Beast. “They got the information. They just didn’t trust it. And they did sit on it, there’s no doubt about that.”

The Islamic State group, formerly known as either ISIL or ISIS, beheaded Foley in August. He was the first American killed by the militants. The Obama administration later disclosed the failed attempts to save the slain journalist, but dismissed suggestions the U.S. was slow to act.

“I can assure you that we have done everything that we can possibly do to try to bring home our hostages,” U.S. National Security Adviser Ben Rhodes said during a press conference last year at Martha’s Vineyard, Massachusetts, according to the Daily Beast. “It’s an incredibly difficult circumstance in a place like Syria, again, where you have such a violent conflict raging. But we’ve used all of our military, intelligence, diplomatic resources that we can bring to bear to try to pull a thread to find out where our hostages are; to try to rescue them when we saw an opportunity; to try to work with any country that might have any means of locating them.”

French officials reportedly provided the U.S. with intelligence about the captives’ locations as early as March, and yet the White House did not act on the information. “That was part of our frustration,” Foley’s mother Diane Foley told the Daily Beast. “Very specific information was available as early as mid-March. And that’s what’s been so tough for us as families, because apparently they were held in the same place all those months.”

Foley’s family said in September they were threatened by a U.S. official with charges of supporting terrorism should they pay a ransom to their loved one’s Islamist captors, ABC News reported at the time.

The parents of Sotloff -- who was beheaded in September -- have shared the Foley family’s frustration, saying the U.S. did not do enough to save either of them.

The rescue effort to save Mueller has also come into question. The Islamic State group claimed last week the 26-year-old aid worker was killed in a Jordanian airstrike targeting the group’s stronghold in Raqqa. Jordan launched airstrikes against the militant group the day after it released a video showing a Jordanian pilot being burned alive.

The terrorist group showed a photograph of a bombed building where Mueller was allegedly held. European officials told the Daily Beast the building was a known hostage location and that this information was shared with the U.S. and Jordan. Shortly after Mueller’s parents confirmed her death, the Pentagon said Tuesday that Mueller was killed not by a Jordanian airstrike but by the Islamic State group.