Topeka ? Drug enforcement agents say a field with more than 1,000 marijuana plants was seized after a clandestine growing operation was discovered in southeast Shawnee County.

Shawnee County sheriff’s Sgt. Jay Simecka says an anonymous tip led investigators to the extensive outdoor marijuana operation in a large wooded area.

Officials say the operation apparently was operating for at least six months.

The estimated value of the marijuana plants is about $1.5 million.

The sheriff’s office says the landowner apparently did not know about the operation.