YARMOUTH, Maine (AP)   An environmental group is threatening to sue a Maine town over a broken fish ladder on the Royal River.

The Portland Press Herald reports the Maine Conservation Law Foundation was joined by four local environmental groups in June that demanded Yarmouth and the owner of a mill fix the fish ladder. The Conservation Law Foundation had previously issued a notice of intent to sue both parties.

Environmental advocates say the ladders and dams are old and restricting activity on the Royal River. They say the Bridge Street dam is filled with branches, trash and other debris.

Yarmouth officials voted to study the dams in 2009.

Foundation director Sean Mahoney says the town needs to figure out if it will fix the fish passage or remove the dams.