BUTLER, Mo. -- Investigators found a meth lab on the property of a high school athletic director already accused of buying too much cold medicine containing pseudoephedrine -- the ingredient used to make the drug, investigators said on Thursday.

The Bates County sheriff took Butler High School athletic director Mitch Warmbrodt, 46, into custody at about 9:30 a.m. on Wednesday at the high school on a Vernon County warrant for acquiring more than 9 grams of the controlled substance, ephedrine, according to a news release.

The sheriff took Warmbrodt to the Bates County Sheriff's Office, and while he waited to be arraigned, investigators uncovered a "clandestine methamphetamine lab" on his property, according to the news release.

Warmbrodt bought more than 12 boxes of Sudafed in a month at Wilkinson Pharmacy in Rich Hill, Mo., and at the Wal-Mart Pharmacy and Hometown Pharmacy in Butler, according to court records.

Customers have to sign for Sudafed, and buying that much in such a short time period is against the law.

Warmbrodt bought some of the cold medicine at Marcus Wilson's pharmacy, and investigators took the log Warmbrodt signed to use as evidence, Wilson said.

In addition, investigators said they found a meth lab in a barn near Warmbrodt's house, and prosecutors could file charges of manufacturing methamphetamine against Warmbrodt and another man.

Warmbrodt's wife is the principal of an elementary school, but prosecutors didn't file any charges against her. No one answered the door at Warmbrodt's house on Thursday, where he and his wife live with their two children.

His arrest was part of a major drug crackdown in which federal and local officers made arrests in several drug operations. The sheriff planned to meet with school board members on Thursday to determine whether to investigate anyone else.