SANTA ROSA (AP) — Federal investigators are demanding records related to a Northern California county’s medical marijuana permitting program.

Mendocino County Sheriff Tom Allman told local news outlets this week that county officials received a subpoena in October from the U.S. attorney’s office in San Francisco.

The records request is connected to the county’s now-canceled program to authorize certain marijuana growers to grow as many as 99 plants, exceeding the local limit of 25 plants. The permitting process garnered more than $800,000 in county fees in its two-year existence.

Applicants paid $1,500 for a permit. They also were responsible for a monthly inspection fee of about $500 plus an additional $50 each for individually numbered zip ties designed to identify every authorized plant. The funds were used by the sheriff’s department to monitor the program.

Officials canceled the program in January after the U.S. attorney’s office threatened legal action. The office threatened to hold individual county officials who supported the program personally responsible. Marijuana remains illegal in all forms under federal law.

The county collected information that included growers’ names and the patients they were serving.

“The question is, why is the federal government using resources in this way when people are growing all over the state in a similar fashion?” Kris Hermes, a spokesman for the national group Americans For Safe Access, told the Santa Rosa Press Democrat. “Why is there such determination to undermine what Mendocino County was trying to do, and hopefully will continue to do in the future, once it gets the federal government off its back?”

The sheriff said he is not sure why federal prosecutors want the records. He also said he is frustrated with fruitless attempts at getting legal guidance from the U.S. attorney’s office in San Francisco on how to reconcile California’s legalization of medical marijuana with the federal blanket ban on the drug.

The U.S. attorney’s office declined to comment Wednesday.