At the end of April, Pakistani officials told CBS News that 10 men linked to the Taliban had been sentenced to 25 years in prison for the attempted assassination of teen activist Malala Yousafzai in the country's Swat province.

Friday, however, it emerged that eight of those men were subsequently set free -- and may never have been convicted in the first place -- by a secret military court that found the evidence against them "had gaps."

A senior Pakistani intelligence source confirmed to CBS News' Farhan Bokhari that only "two of the ten suspects have been convicted," and said the other eight "have been freed because they did not carry out the shooting."

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Officials from the Pakistani Embassy in London told CBS News later Friday that the eight freed suspects were acquitted because of a lack of evidence against them.

The current whereabouts of the eight men freed by the court, however, remained a mystery.

The two convicted suspects have been sentenced to life imprisonment, according to the embassy in London.

It was The Mirror tabloid of Britain which first reported the development in the story on Friday, saying it had tried to track down the 10 convicts in Pakistani prisons and uncovered the apparent inconsistency.

The official, who spoke to CBS News on the condition of anonymity, said the eight men released had been "held on charges of facilitating this crime, but in the end the evidence had gaps which is why they were freed."

Yousafzai was attacked in 2012 -- shot at close range in the head -- by militants for speaking out in support of girls' education. She was critically wounded in the attack, which took place on a bus as she returned from school in her native city of Mingora, in Pakistan's northern Swat valley. She was subsequently taken to Britain for specialized medical care.

Yousazai went on to gain international recognition for her bravery and last year became the world's youngest recipient of the Nobel Peace Prize.

The details around the two original suspects who have in fact been convicted and imprisoned also changed Friday, with officials telling the Mirror and the BBC that they were the men who actually carried out the attack.

At the end of April, officials said the 10 had been convicted essentially as accomplices, and that the two primary suspects in the case were still at large; identified then as Ataullah Khan, an Islamic militant believed to have pulled the trigger, and Maulana Fazlullah, leader of the Pakistani Taliban. Both men were purportedly believed to be hiding in Afghanistan.

"We are actively pursuing those two," a senior government official from Pakistani Prime Minister Nawaz Sharif's office told CBS News in April. "Sooner or later, both of them will be caught or killed."

That official could not be reached Friday by CBS News for comment.

The trial which led to the two convictions which appeared Friday to actually have been carried out -- and the eight other reported convinctions -- were handed down by a Pakistani court which conducted the trial in complete secrecy, without any members of the media present.

Word of the convictions in April took the journalists of Pakistan, and the world, largely by surprise as there had been no talk of suspects even being in custody. Islamabad had come under increasing pressure to find and arrest the perpetrators, especially given the huge attention gained by Yousafzai's Nobel Prize win.