Multiple crashes on the 99 are leading to slowing and complete blocks Tuesday morning. 

According to the California Highway Patrol, a big rig jack knifed just south of White Lane on the northbound 99 around 6:30 Tuesday morning. That's led to the closure of all northbound lanes in the area. 

In the area of California Avenue, a crash into the center divider has led to the closure of two lanes on the northbound side of the 99. 

There is no timeframe as to when the scenes will be clear.