A 26-year-old man has been charged with concealing the killing of a 16-year-old girl whose body was discovered three days after she was reported missing last month in downstate Putnam County.

Richard A. Henderson, of Standard, was charged with concealment of a homicidal death, the Putnam County Sheriff’s Office said Tuesday.

The case was still under investigation and authorities said they expected to add more charges later.

Diamond Bradley was found about 1 p.m. Jan. 27 in a ditch alongside County Highway 850 North in Gravnville Township, the sheriff’s office said. She had been stabbed multiple times and her death was ruled a homicide.

Authorities believe Henderson met Bradley on the internet and the two agreed to meet the morning of Jan. 24. Henderson picked Bradley up near her home in Spring Valley and drove her into Putnam County. At some point, Henderson stabbed Bradley to death, the sheriff’s office said.

Henderson was linked to Bradley through an investigation that included tracking Bradley’s cellphone and the use of surveillance cameras, the office said. Nearly 20 law enforcement agencies worked on the case.

Henderson was taken into custody Monday and was being held in the LaSalle County Jail ahead of his arraignment in Putnam County.