By Erica Ho | TIME

It’s hard to believe there’s much mystery still surrounding the Hindenburg disaster. After all, the largest airship in history was not only filled with hydrogen — a notoriously combustible gas — but the horrific incident was one of the first disasters to be captured in real time — on film, in photos and on the radio (not to mention immortalized in Led Zeppelin album cover art).

But 76 years on, scientists still haven’t been able to definitively say what actually caused the spectacular 1937 explosion as the German airship attempted to dock in Lakehurst, N.J.

An investigation into the incident concluded that a spark had ignited leaking hydrogen, reports The Independent, but the cause of the spark or the leak were never determined. Possible theories ranged from lightning to a saboteur’s bomb, planted in an attempt to destabilize Hitler’s Nazi regime.

But now, a team at the South West Research Institute in San Antonio, Tex. led by British scientist Jem Stansfield, believes it has an answer. According to the Independent, the scientific team explains how it happened in an upcoming British documentary:

The airship had become charged with static as a result of an electrical storm. A broken wire or sticking gas valve leaked hydrogen into the ventilation shafts, and when ground crew members ran to take the landing ropes they effectively “earthed” the airship. The fire appeared on the tail of the airship, igniting the leaking hydrogen.

‘I think the most likely mechanism for providing the spark is electrostatic,’ said Mr Stansfield. ‘That starts at the top, then the flames from our experiments would’ve probably tracked down to the centre. With an explosive mixture of gas, that gave the whoomph when it got to the bottom.’