HARRISBURG — An enforcement blitz that focused on trucks hauling wastewater from Marcellus Shale drilling operations generated hundreds of citations and warnings and forced 131 water-hauling trucks off the road, Pennsylvania State Police said.

The department's Operation FracNET, named after the drilling process known as hydraulic fracturing, inspected 1,137 trucks over three days last week. In all, 250 commercial vehicles were placed out of service, along with 45 drivers. Twenty-three of those drivers were operating trucks that haul wastewater from drilling sites, police said.

State police spokeswoman Lt. Myra Taylor said Thursday many of the violations involved exceeding weight restrictions and equipment problems, including malfunctioning brakes. She said inspectors did not recall any water tanks leaking, but could not rule it out without reviewing the citations. Inspectors issued 669 traffic citations and 818 written warnings

"What's disappointing are the numbers, because they're high," Taylor said. "We want voluntary compliance. That's sometimes a difficult thing to do, but we don't care."

Troopers worked with the Public Utility Commission, the Department of Environmental Protection and federal transportation official on the crackdown, which concentrated on vehicle problems that could lead to crashes.

Taylor said the department previously contacted Marcellus Shale businesses about issues related to their operations.