Unless I missed something, no one died. That seems to be a minor miracle. I don't know how long the tunnel is but I'm surprised people didn't die of smoke inhalation. The official story does seem a little weird. It also seems to be a little bit unsafe to drive missiles with rocket fuel through the tunnel.
I have to drive those tunnels during my monthly trips to Korea. Yep, in Daegu/Taegu. They're very well vented for situations just like this. Some years ago, a tunnel in Holland/Sweden/Switzerland (?) caught fire and 20-some people died from the smoke.