Boston (SmartAboutHealth) - An unknown strain of the swine flu has popped up with two cases in California.

Investigators are looking into two cases of the unknown strain of the swine flu.

The two cases popped up in the San Diego, California area, with a 10-year old boy and 9-year old girl being infected.

U.S. Centers for Disease Control and Prevention (CDC) investigators have been working to unravel the causes of this unknown strain.

They do not appear to be related as neither came in contact with any pigs as of late, nor each other.

In the last 3 years there have been 12 human cases of swine flu being investigated.