WASHINGTON — Detectives checking a tip about child pornography in Charles County, Maryland, say their investigation led them to a veteran officer in their own department.

Officer Alexander C. Sullivan, 37, of King George, Virginia, who’s suspected of uploading child pornography on his cellphone, was arrested Monday and charged federally with possessing child porn.

In a statement released Tuesday, the Charles County Sheriff’s Office said it was checking a tip it received about child pornography being uploaded from a specific cellphone number when detectives recognized Sullivan’s name and phone number.

Federal prosecutors said the forensic investigation is still ongoing, but a preview of materials on Sullivan’s phone appeared to show more than 200 images and five videos containing child pornography.

Sullivan, who has been with the department for 10 years, has been suspended without pay pending the outcome of his criminal trial, the sheriff’s office said in the statement.

Sullivan faces a maximum of 10 years in prison. He was in U.S. District Court in Greenbelt, Maryland, Tuesday afternoon, where he was released to home detention with electronic monitoring.