Insecure load?

I was reading the paper this morning and there was a story about a woman who's car was hit by a runaway Jeep. Apparently it had come loose from a tow truck and freewheeled across the street until it hit something. The paper reported the tow truck driver was charged with an 'insecure load'. That made me giggle.

To me, the load should be 'unsecure' as I'm sure the load doesn't have low self esteem. However, so far I haven't been able to find out how the actual law is written but it seems both are used.

What do you think it should be?
Do you know the correct wording?

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Edited: The correct word is actually "insecure".
"Operating vehicles with insecure cargo prohibited" = here is how it's written. Huh.Interesting.