Ncis: Los Angeles star Daniela Ruah is a new mum.

The actress, who plays Special Agent Kensi Blye on the hit show, and her fiance David Olsen welcomed their first child, River Isaac Ruah Olsen, on Monday (30Dec13).

Ruah tells her son is "healthy and strong," adding, “We are so happy, so thankful and feel so blessed to have brought him into the world.”

Olsen is Ruah's Ncis co-star Eric Christian Olsen's brother and stunt double.