Mo. Rev. Stat. § 260.525: Investigation, no person to refuse entry — search warrant to be issued.

No person shall refuse entry or access for the purpose of investigating or responding to hazardous substance emergencies of an authorized representative of the department who presents appropriate credentials, nor obstruct or hamper the representative. A suitably restricted search warrant, upon showing of probable cause in writing and upon oath, shall be issued by any judge or associate circuit judge having jurisdiction to any such representative for the purpose of enabling the representative to investigate or respond to hazardous substance emergencies.