CONCORD, N.H. — Four more arrests have been made in connection with a broad criminal investigation into physical and sexual abuse allegations at New Hampshire’s youth detention center.

Stanley Watson, Victor Malavet, Trevor Middleton and Jonathan Brand together have been charged with 15 counts of sexual assault between 1997 and 2007, the attorney general’s office said Wednesday.

They are among 11 former workers at the Youth Development Center in Manchester who have been arrested this month. The seven others have been charged with either sexual assault or acting as accomplices to assault from 1994 to 2005.

The center, now called the Sununu Youth Services Center, has been the target of a criminal investigation since 2019, as well as a lawsuit in which more than 200 men and women allege they were physically or sexually abused as children by 150 staffers from 1963 to 2018.

The four men arrested Wednesday are due in court Thursday. It is unknown whether they are represented by attorneys.