Members of Congress were visibly frustrated Wednesday as they questioned an administration official about the slow pace of action on keeping invasive species out of the Great Lakes.

"Here you have these international boats dumping these critters all over the place and you can't do anything," Rep. Candice Miller, R-Harrison Township, said at a hearing by the House Transportation and Infrastructure Subcommittee on Water Resources and Environment.

The hearing was called to examine the problems posed by the zebra mussel, the sea lamprey and other creatures that threaten native species by gobbling up their food.

"It's an ecological and environmental disaster," said Rep. Vernon Ehlers, R-Grand Rapids, a scientist and longtime champion of Great Lakes issues.

Benjamin Grumbles, assistant administrator for water at the Environmental Protection Agency, told lawmakers his agency and others are researching how nonnative species enter the lakes so they can come up with a way to keep them out.

"We all recognize we need to do much more in terms of the invasive species threat," Grumbles said.