A horse that was first past the post in the opening race at Seymour on Thursday was disqualified after jockey Daniel Moor weighed in light.

The Anthony Freedman-trained Zuhayr, which started $4.80, crossed the line first in the Bar Landy Restaurant Maiden Plate (2015m) but stewards disqualified the galloper before correct weight was declared.

The Danny O'Brien-trained Al Command was elevated to first with Bench And Bar and Encosta Rossa filling the minor placings.

An inquiry into how Moor weighed in light has been opened by stewards.

It is the second time in recent months where Moor has weighed in light, resulting in a horse being disqualified after being first past the post.

In a race at Wangaratta last September, Moor weighed in light on the David Hayes-trained Aajwaad after it was established a lead bag Moor had weighed out with was inadvertently not included in the gear when a stable representative saddled up the horse.

Moor was fined $1000 on that occasion and Hayes $3000.