Law enforcement officers are on alert as drug smugglers try to use the post office holiday rush to get their goods in the mail.
"The amount of volume that's going through the postal system right now would make it easier for certain packages to get through," one Cameron County investigator said.
He and his partner do not want to be identified.
They are undercover at the Los Ebanos Post Office in Brownsville.
They're trying to detect drug traffickers.
"People want money... They need money to buy gifts," one investigator said.
More than 54,000 pounds of marijuana alone were seized by Cameron County sheriff deputies as part of a two-year federal grant that's set to expire in December.
The department will lose a dozen deputies who solely work drug trafficking cases which include narcotics through the mail.
Manpower is the biggest set back for most agencies who work these types of cases.
The investigators admit they're outnumbered.
But the game of cat and mouse can tip in their favor with extensive training.
Officers don't want to tip off dope runners as to what key indicators they look for, but say one red flag is when people purchase empty mailing boxes.
"They usually purchase empty boxes, load them up and come back to the post office and it gets overlooked and sent in right away."
Officers end up following an out-of-state vehicle.
The driver made a large purchase of empty boxes.
The SUV weaves in and out of traffic, often times at a high rate of speed.
It's believed the boxes could be dropped off at a stash house to be loaded up with drugs.
"Chances are they are trying to get the merchandise out of the Valley... And send it up state to Georgia ... It's a well known state for trafficking drugs."
The unidentified driver pulls into a WIC store and parks in the back.
These two feel like their cover is blown. One of them calls in the license plate of the suspicious vehicle for later review and the tail is called off.
"It's always a good day when you can get a drug load off the streets," the investigator said. "This is just an example of us doing our part to get the load off the streets."
Back at the post office, suspicious activity leads an officer to call one man back outside the building.
"Did you package it yourself," he asks the man. "Can you open it for me?"
If a package comes into question, people are asked to sign a consent form.
If denied, authorities can call in a K-9 to sniff out the contents.
But even before Jorge Castellanos agrees to open his box, the officer realizes there are no drugs inside.
"The weight of the box... It's too light to indicate dope... So there was no reason to continue," the investigator said.
Jorge is shocked to learn his box is fingered as possibly suspect but agrees with the officer's work.
"It's a pretty good way of doing it... Check people around with packages," he says. "I have just some clothes that didn't fit in mine... A Christmas gift... So I'm returning it to get my money back."
There are no drug busts on this afternoon, but as the holiday season ramps up, officers know it's only a matter of time before someone gets caught.