Semi-truck jackknifes in violent crash on 5 Freeway northbound near Pacoima

PACOIMA, Calif. (KABC) -- A serious crash involving multiple semi-trucks and what appeared to be a pickup truck caused a massive backup on the 5 Freeway in Pacoima during rush hour Friday morning.

The accident happened around 5 a.m. in the middle northbound lanes just before the 118 Freeway.

AIR 7 HD was over the scene, where a semi-truck had jackknifed, leaving a string of debris on the major freeway. It appeared several vehicles had run over the debris, which was spewed across the roadway. Three other semis were also involved.

Traffic was backed up for miles until lanes were reopened hours later.

It was not immediately clear if any injuries were reported.

The cause of the crash remains under investigation.