A homemade explosive device detonated outside a Planned Parenthood clinic in Grand Chute, Wisconsin on Sunday night.

Police are still looking for whoever left the device, which exploded around 7:30 p.m. and caused little damage to the building. Nobody was injured.

The attack is one of a string across the U.S. in recent months.

Amid a heated debate over funding for Planned Parenthood last month, the Fort Worth offices of Texas State Senator Wendy Davis (D) — a strong supporter of the female health program — were attacked with two firebombs. Another clinic in the Dallas area was attacked in a similar manner by a separate person last July.

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This video is from NBC 26 in Grand Chute, Wisconsin, broadcast Sunday, April 1, 2012.

Photo: Shutterstock.com, all rights reserved.