A new government report says the number of children in the U.S. foster care system has increased for the fourth year in a row, due largely to an uptick in substance abuse by parents.

The report, issued annually by the Administration for Children and Families of the Department of Health and Human Services, shows that 437,500 children were in foster care by the end of fiscal year 2016. A year earlier the number was 427,400.

The foster care population peaked at 524,000 in 2002 and dropped to about 397,000 cases by 2012.

Government data also shows that drug abuse by a parent was a factor in 34 percent of the cases in 2016, up from 32 percent in 2015. About 92,000 children were removed from their homes due to the substance abuse of at least one parent.

Indiana, Florida, Georgia and West Virginia, all grappling with the opioid crisis, are among the states with the largest one-year increases in the number of foster care children.

"The continued trend of parental substance abuse is very concerning, especially when it means children must enter foster care as a result," said Steven Wagner, acting assistant secretary for children and families at ACF.

The data also reveals an increase in the number of adoptions from the U.S. child welfare system, from 54,000 in FY 2015 to 57,000 in FY 2016.

The ACF recently awarded 18 grants totaling more than $12.5 million to improve the outcomes of children affected by a parent's or caregiver's substance abuse.

As the Associated Press points out, the federal report does not address the ability of states to deal with the increasing numbers of foster children.

In a recent report by the Chronicle of Social Change, a nonprofit publication, finds that as the number of American children in foster care increases, there is a concurrent shortfall in the number of foster homes to accommodate them.

Among its key findings:

"At least half of the states in the U.S. have seen their foster care capacity decrease between 2012 and 2017. Either these states have fewer beds and more foster youth, or any increase in beds has been dwarfed by an even greater increase in foster children and youth."Copyright 2017 NPR. To see more, visit http://www.npr.org/.