A New York State assemblyman from the Hudson Valley was charged with marijuana possession after he was stopped for speeding, the authorities said on Friday.

The assemblyman, Stephen M. Katz, 59, a Republican from Mohegan Lake, was found with a “small bag” of marijuana when stopped on Thursday, the State Police said in a statement. Assemblyman Katz was charged with unlawful possession of marijuana, a violation that is punishable by a fine of up to $100.

In a statement, Mr. Katz said the episode was “unfortunate.”

“This should not overshadow the work I have done over the years for the public and my constituency,” he said, adding, “I am confident that once the facts are presented that this will quickly be put to rest.”