ANDERSON, Calif. -

A crash involving at least four vehicles tied up traffic on Interstate 5 south of Redding on Wednesday morning.

It happened on the southbound side of the freeway just south of the North Street exit around 11:30 a.m.

According to a witness, the crash was the result of a chain reaction in the left lane. A pickup truck suddenly slowed, causing the vehicles behind it to pile into each other.

At least four vehicles were involved, and at least one person - a pregnant woman - was taken to the hospital, according to the witness.

Traffic was reduced to one lane while the incident was cleared, causing backups on the interstate during the investigation.