POLICE have arrested a man and a woman after four adopted children were found locked inside wooden boxes in “deplorable conditions” on a property in the US.

Officers raided the home in Farmington, Missouri and discovered three girls and a boy barricaded inside specially constructed boxes held together by plywood and screws.

Laura Cheatham and Daryl Head, both 38, were arrested after an anonymous caller contacted authorities to report the alleged abuse on Tuesday, Fox News reported.

St Francois County Sheriff Daniel Bullock told reporters he feared the children, who are aged between six and 12, had been imprisoned inside the boxes for weeks.

The containers were “smaller than a jail cell” with no access to water, toilets, windows or light and smelled strongly of urine.

“I’ve seen some pretty nasty things but nothing this deplorable,” Sheriff Bullock said.

Police documents tendered to court said Ms Cheatham originally adopted the four youngsters with her estranged husband Richard. Ms Cheatham had been living at the property with the children for several weeks but it was not clear what her relationship was with Mr Head.

Police will allege that when they arrived, Mr Head initially denied them entry. When they forced their way inside, Ms Cheatham was trying to free the children by removing the plywood that had been screwed on to the top of the boxes.

Neighbours have since told police that they regularly saw the children doing manual labour, including sawing plywood they believe was later used to keep them captive in the boxes.

Despite the conditions they were allegedly subjected to, the children were found to be in good health.

Ms Cheatham and Mr Head were both charged with four counts of second-degree kidnapping and endangering a child.

Their bond was set at $US2 million ($A2.7 million) each. The children have been placed in government care.