SPRINGFIELD, Mo. -- Interstate 44 has long been a favorite route of drug dealers trying to move their cargo from east to west, but law enforcement officers trying to stop the flow have seen more drugs -- and more variety -- this year.

Since December, some major drug busts along I-44 between Joplin and Rolla have included 3,000 pounds of marijuana, 140 pounds of cocaine and the country's largest recorded seizure of PCP, the Missouri State Highway Patrol said.

"It's not just limited to marijuana and cocaine," said Sgt. Dan Bracker, spokesman for Troop D in Springfield. "There's heroin, pills, pseudoephedrine. You name it, and it's probably moving up and down that interstate."

A week before Christmas, a minivan traveling west on I-44 in Greene County was carrying 80,000 tablets of Ecstasy. Two Canadian men were later indicted on federal drug charges.

Officers also are finding elaborate mechanisms drug runners are using to conceal their cargo. A sport utility vehicle stopped in Jasper County last month had 44 pounds of cocaine inside a speaker box. The door to the hidden compartment was hydraulically controlled, the patrol said.

And 40 gallons of liquid PCP intercepted at a weigh station in Joplin was sealed in unlabeled one-gallon cans.

"If these guys took all that ingenuity and craftiness and applied it to a legitimate business, they'd be multi-millionaires," Bracker said.

The highway patrol says the amount of marijuana seized statewide has increased from 10,500 pounds in 2003 to 15,143 pounds in 2005 -- a 44 percent increase over three years.

Seizures of cocaine, however, declined 30 percent from 2003 to 2005. But more meth -- 4.5 pounds -- has been seized already on I-44 since December than the 4 pounds seized statewide in 2004.

And the amount of PCP has skyrocketed, thanks to the record-setting bust in March. Only 1 ounce of PCP was reported seized in 2005 statewide, compared with the 40 gallons already seized on I-44 this year.

In 2005, there were 311 drug interdiction arrests on Missouri highways. That's a 117 percent increase over 2003 -- though the number dropped from the 402 arrests reported in 2004.

Bracker said many drug busts still start because the drivers disobey traffic laws. Earlier this month, the driver of a rental truck traveling east on I-44 in Greene County was pulled over for following too closely. Police say they found 1,246 pounds of marijuana in the truck.

Before a 2000 U.S. Supreme Court ruling, some Missouri law enforcement agencies set up checkpoints along known drug-trafficking routes. But the court ruled that such roadblocks subjecting all cars to drug-sniffing dogs violated the Fourth Amendment.

"We've just had to adapt and change our methods so we make sure we're doing things according to those rulings," said Phelps County Sheriff Don Blankenship.

Some agencies work around the ruling by posting signs that warn drivers of a nonexistent drug checkpoint ahead. Cars that immediately leave the interstate are then stopped for probable cause.

For the most part, large-scale drug shipments originate in the southwest and move east, said Eric Siweck with the U.S. Drug Enforcement Administration office in Springfield.

Drugs intercepted along I-44 are typically headed toward St. Louis, although the recent cache of Ecstasy was going west, Siweck said.

The patrol and county sheriff's departments generally handle the drug arrests, Siweck said, while the DEA's role is to try and trace seized drugs back to their source and dismantle drug organizations.

Bracker concedes the drugs seized along I-44 represent only a "small percentage of what's out there," but he said that doesn't mean the effort is wasted.

"Our philosophy is no matter what percentage we're taking out, we're taking it out of your streets and neighborhoods," he said.