Safety or Touchback?

[chiefgil]

B2 intercepts A's pass at A's 7. When contacted by A1, B2 fumbles the ball which is caught in the air by A2 at his own 4 yard line, while was moving toward his own goal line. A2's momentum carries him into his own end zone, where he falls down.

SAFETY: score two points for B

OR

Daad ball at the spot (4 yard line) where A regained possession