FRASER, Mich. (AP) — Huge sinkholes that opened last week on streets in New York City, suburban Atlanta and San Francisco exemplify a phenomenon that is prompting growing alarm across the U.S., including Iowa.

Sudden-appearing caverns are happening in places where they once were rare. Unlike most earthen collapses in the past, the new cave-ins are being caused by crumbling water and sewer pipes rather than unstable geology.

A review by The Associated Press of recent media coverage showed that sinkholes related to failing infrastructure occurred at a rate of one every four days in places as varied as Chicago, Los Angeles, Hoboken, New Jersey, Sioux City, Iowa, and Seattle.

A San Antonio woman died in December when she drove into a sinkhole that opened when a sewer line ruptured.