CROSSROADS, N.M. (AP) — The U.S. oil and gas production boom of the past decade has an unwanted side effect: Millions of gallons of briny wastewater have spilled onto land and flowed into waterways, often doing severe damage.

An Associated Press analysis of state and federal record finds some 21,651 spills of oilfield wastewater between 2009 and 2014. They add up to more than 175 million gallons. And officials acknowledge many releases are never reported.

The spills happen primarily because of human error and equipment failures such as ruptured pipelines, overflowing tanks or illegal dumping.

Experts say wastewater spills can be more environmentally harmful than oil spills. The salty byproduct turn can land into barren moonscapes where plants can't grow.

Oil industry officials say they're trying to reduce the number of spills.