UPDATE (5:12 a.m.): Kern County Sheriff's officials say a man who was possibly mentally distressed was on the overpass at Olive and the 99. After about 3 1/2 hours of negotiating with the man they were able to taken him into custody. 

KCSO says the 99 will be fully open in the next 10-15 minutes. 

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Both sides of Highway 99 near Olive Drive are shut down Monday morning due to heavy law enforcement activity.

The California Highway Patrol has been at the scene since about 2:30 a.m.

It's not known how long traffic will be shut down.