We present multi-color light-curves of the optical afterglow of GRB 000926 .
Beginning \sim 1.5 days after the burst , the light-curves of this GRB steepen measurably .
The existence of such achromatic breaks are usually taken to be an important observational signature that the ejecta are not expanding isotropically , but rather have a collimated jet-like geometry .
If we interpret the data in this context , we derive an opening angle of 5 ^ { \circ } , which reduces the energy release compared to an isotropic model by a factor of \sim 275 , to 1.7 \times 10 ^ { 51 } erg .
To fit the data with a simple jet model requires extinction along the line of sight .
The derived A _ { V } is in the range 0.11 – 0.82 mag , depending on the adopted extinction law and whether the electrons giving rise to the optical emission are undergoing synchrotron cooling or not .
Since this is in excess of the expected extinction from our Galaxy , we attribute this to the GRB host .
We note that this extinction is typical of a galactic disk , and therefore the event likely took place in the disk of its host .