Two people died when the small plane crashed near an airstrip in Arvika after one of its wings fell off as the plane was about to land.
Investigators have learned that the plane was built in part by high school students enrolled in a vocational programme at Kattegattgymnasiet in Halmstad in western Sweden.
The plane was never completed, however, and about a year ago, it was sold to four members of a flying club in Arvika, who completed construction of the Zenair CH 701.
On Monday, education officials in Halmstad sent background information about the plane to police in Värmland, who are heading the investigation.
According to reports from the accident site, the plane was flying at a height of between 50 and 75 metres when a wing came loose, causing the plane to crash.
Kattegattgymnasiet bought the plane as a ready-to-assemble model before selling it to the flying club members for 135,000 kronor ($20,000).
"When we examined the wreckage we discovered that the construction of the wing-spar was missing three bolts that were supposed to be steel," investigator Staffan Ekström of the Experimental Aircraft Association (EAA) told the Hallands Nyheter newspaper.
"They were replaced with aluminium rivets."
Ekström believes the accident was caused by the use of the rivets, which failed to withstand the forces put on the wings during the plane's flight.
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The investigation into the accident remains ongoing, however, with police yet to determine whether or not to classify it as a manslaughter probe, which would likely be directed at the high school where the plane was partially built.