WASHINGTON - More than 1 million cases of child abuse or neglect were documented by the states in 1994, but the actual number of children mistreated may have been three times that, federal officials said yesterday. Substantiated cases of child abuse or neglect increased 27 percent during the five-year period beginning in 1990, the Department of Health and Human Services said.

There was little change between 1992 and 1994, however, with the number of verified cases hovering just over 1 million.

''There has been an increase in child abuse and neglect since 1990 which is attributed in part to drug use and an increase in drugs that are highly addictive and cause severe behavioral changes, such as crack cocaine,'' said Michael Kharfen, a spokesman for the department.

In the latest report, 53 percent of the children studied suffered neglect. Twenty-six percent were physically abused, 14 percent were sexually abused, 5 percent were abused emotionally and 22 percent suffered other types of mistreatment. Some victims suffered more than one type of abuse.

The report by the National Center on Child Abuse and Neglect was based on statistics gathered from 47 states and the District of Columbia. But federal officials believe many cases of abuse and neglect are not verified and reported by the states. The states said they investigated more than twice as many child abuse allegations than they verified - about 2.7 million in 1994.

Other studies indicate the actual number of abused and neglected children may be much higher than the number the states were able to substantiate, said Mary Jo Bane, HHS assistant secretary for children and families. Preliminary results of a study ordered by Congress found 2.9 million children were abused or mistreated in 1993. The National Incidence Study of Child Abuse and Neglect receives information from private professionals who have contact with abused children, in addition to state officials.