PROVIDENCE, R.I. — An algae bloom is forcing the closure of most of Narragansett Bay in Rhode Island to shellfishing.

The state Department of Environmental Management says this is the first time that harmful algae has prompted a shellfishing closure in Rhode Island.

Starting Friday morning, shellfishing was barred from Conimicut (koh-NIH'-mih-cut) Point in Warwick south to the mouth of Narragansett Bay.

The agency says a toxic phytoplankton caused the harmful algae bloom.

Many tributaries to the bay are also closed. Mount Hope Bay and the Kickemuit River are closed but scheduled to open at noon Saturday.

The agency says it's working with the Department of Health to monitor shellfish for the toxin domoic acid, which can cause amnesiac shellfish poisoning.