More than 40 years after the plane crash that killed him, new details are starting to emerge on the death of Yuri Gagarin, the first man in space.

Acording to fellow cosmonaut Alexey Leonov, an "unauthorized" plane flew too close to Gagarin's fighter jet, sending it spinning and ultimately causing it to crash near the town of Novoselovo, approximately 50 miles (90 km) from Moscow.

Following the event, a government investigation, of which Leonov was a part of, resulted in a report stating that the plane lost control when trying to avoid a "foreign object," such as birds.

However, according to Russia Today, on the conclusion of the original investigation, Leonov said that such a statement is "believable to a civilian - not a professional."

Now, years later, Leonov is speaking out after years of struggling to gain permission to disclose the details in his friend's death.

According to a declassified report, the fault belongs to a Su-15 fighter jet that broke with flight directions, though Leonov has agreed to not disclose the pilot's name.

"We knew that a Su-15 was scheduled to be tested that day, but it was supposed to be flying at the altitude of 10,000 meters or higher, not 450-500 meters," Leonov told the Russian news outlet. "It was a violation of the flight procedure."

A team was sent to the site to excavate the remains of the plane, but he was not there.

At first, those on the scene took this as hopeful evidence - perhaps, they thought, he ejected himself successfully.

"We sent a battalion of soldiers who combed the forest for the whole night," Leonov said. "They shouted so that he could hear them, but all they found were remains of a balloon."

The next day, they found Gagarin's body, which Leonov was able to identify by a dark mole on his neck that he had spotted just three days before.

As to why the event was hidden under so much secrecy, Leonov offers one possible suggestion.

"My guess would be that one of the reasons for covering up the truth was to hide the fact that there was such a lapse so close to Moscow," he said.

Meanwhile, the death had great impacts on Valentina Tereshkova, the world's first woman in space who celebrated 50 years since her flight on June 15.

"They forbade me from flying ever again, even piloting planes," she said at a press conference at UN headquarters in Vienna. "The repercussions of the death of one cosmonaut were so great that they wanted to keep me safe."

Holding back tears as she spoke of missing Gangarin, Tereshkova announced the case officially closed.