Why First Epistle to St. John by St. Ignatius of Antioch is considered to be spurious?

Why First Epistle to St. John by St. Ignatius of Antioch is considered to be spurious? Were there any valid reasons put forth to consider it as spurious? The wiki page and this Catholic source only state that this and other epistles by St. Ignatius of Antioch are considered to be spurious, but don't mention any reasons why.