According to Chris Steuber of Scout.com
"A source told me that #BYU FB Manase Tonga signed with the Raiders as an undrafted free agent."
Tonga is a local boy from San Mateo who attended Aragon High.
Here is a great story that I found on him:
At 6-foot and 248 pounds, Tonga is a devastating blocker with powerful drive in his lower body. As a lead blocker in Robert Anae's offense, he was fearless in tracking down and putting a bead on linemen, linebackers, safeties and corners for Harvey Unga. His pass protection is something Anae and position coach Lance Reynolds use as an example, a how-to tape.
Tonga is currently working out daily in Orem with a private trainer, Dave Stroshine, in preparation for the NFL Combine at the end of the month. His draft stock is high, some projecting him as the first fullback taken, according to Stroshine, who also trains former Cougars Fahu Tahi (Minnesota Vikings) and Fui Vakapuna (Cincinnati Bengals).
I think that it is safe to say that anyone who wants to beat him out had better bring his lunch pail to work. IF Tonga can stay out of trouble and really embrace this opportunity he can start right away.