RAPID CITY, S.D. — A Colorado man who said he was delivering hemp to Minnesota when he was arrested in South Dakota has been indicted by a grand jury after his load tested positive for THC, the component in marijuana that produces a high.

A grand jury in Jackson County, South Dakota, last month indicted Robert Herzberg, 41, of Red Feather Lakes, Colorado, on charges of intending to distribute marijuana and possessing more than 10 pounds (4.5 kilograms) of the drug. He also faces charges of ingesting marijuana and cocaine, according to court records. Herzberg is free on $5,000 bond and due in court Nov. 6.

Herzberg told a state trooper he was delivering 300 pounds (136 kilograms) of hemp from Colorado to Minneapolis July 16 when he was pulled over for speeding on Interstate 90. He was arrested after the trooper found “two large white sacks that contained a green leafy substance that looked and smelled like raw marijuana” and field tested positive for the drug.

Prosecutors filed results from the South Dakota state lab that show Herzberg tested positive for THC and cocaine, as well as results from six plant samples that contained more THC than is allowed under federal law.

No amount of THC is legal under South Dakota law. But according to a May memorandum from the U.S. Department of Agriculture, states cannot block the transportation of hemp that contains 0.3% or less THC.

Defense attorney Matthew Kinney said he plans to speak with experts who can explain the reliability of THC testing and whether the amount of THC in a plant can increase over time.

Even if any of his load was above the federal limit, “you can’t get high from this stuff” unless you smoke the entire bag, Kinney said.

Prosecutors also would have to prove that Herzberg knew the plant was marijuana, Kinney said.

“My client thought everything was legal,” Kinney said.