The shipment of marijuana from Mexico into Texas is changing, authorities say, citing the shift away from a seasonal marijuana market and an increase in the quality of the drug.

"What is happening shows a growing degree of sophistication on the part of marijuana producers," explained FBI Senior Agent Bill Vanderland.

"Marijuana is harvested in the fall, beginning in the October time frame, Vanderland said. "It used to be we would see a large influx beginning in October and running into the early part of the year."

In the past several years marijuana suppliers have begun stockpiling the drug after the annual harvest and bringing it into the United States at different times throughout the year, Vanderland said.

Lt. Brian Bogart with the narcotics division of the Midland Police Department said enforcement near the border would peak in the past in the months after harvest time, in anticipation of large shipments leaving Mexico. As suppliers realized this, he said, they began to stagger shipments, stockpiling their product until confident of greater chances in eluding seizure.

Bogart also said the quality of marijuana arriving from south of the border is increasing.

"It's better quality than it used to be and it's getting to be better quality all the time. It's not going to come anywhere near the quality of the hydro weed that's coming out of Canada that has a lot higher THC resin content and is a whole lot more expensive. But marijuana here, granted it is not as good quality as the hydro weed, but it's a lot stronger than weed from years ago."

Bogart said the lower quality doesn't prevent marijuana from finding consumers in the northern parts of the country, explaining that a pound of the drug might fetch $300 locally but could be sold for over $1,000 in New York and areas of the northeastern seaboard.

"You have the high dollar hydro weed coming out of Canada," Bogart said. "But it's not coming out in the quantity that the users in the states use."

The shift from seasonal marijuana traffic complicates enforcement.

"The stockpiling makes our job somewhat more challenging -- you can't really predict it. But the whole trade is changing and we just have to adapt."