Rock County sheriff’s investigators raided a suspected meth lab Monday on Afton Road in Janesville.

Capt. Todd Christiansen of the sheriff’s office detective bureau said no one was there when a tactical team with an armored car arrived to serve a search warrant Monday morning.

No arrests were made, but those believed to have been cooking the meth are being sought, Christiansen said.

They were using the one-pot method, a common technique used in all recent local meth-manufacturing cases, he said.

One person was detained for questioning but not arrested, Christiansen said.

An anonymous tip led investigators to the property, Christiansen said.

The warrant was served at 1101 S. County D, also known as Afton Road, at 11:03 a.m. The property contains several buildings.

Materials used to cook the illicit stimulant methamphetamine were found in a building that is not zoned as a residence, although it looked as though people lived there, Christiansen said.

The property’s owner does not live at that address and is not a suspect, Christiansen said.

A large garbage bag or two of meth-cooking and packaging materials, some of it hazardous waste, were collected, he said.

The state Division of Criminal Investigation Clandestine Lab Team assisted at the scene, as did Janesville firefighters, Mercyhealth’s MD-1 and the FBI Safe Streets Task Force, which provided perimeter security, Christiansen said.

The last meth lab discovered in the county was at a rural residence on County A in the Footville area in April 2017, when two people were arrested. Christiansen said.

A small meth lab was found in January 2016 in an apartment building at 418 St. Lawrence Ave., where two arrests were made.