The U.S. Coast Guard has seized a Mexican fishing boat and detained its five crewmembers in a poaching investigation off Texas.

Coast Guard officials on Monday announced four other boats fled back to Mexican waters. The incident happened Saturday afternoon north of the U.S. and Mexico maritime border and inside the U.S. exclusive economic zone.

A Coast Guard helicopter spotted five boats about 16 miles north of the border. A Coast Guard boat from South Padre Island intercepted one vessel and found 48 dead red snapper.

The five-person crew was turned over to U.S. Customs and Border Protection officials for return to Mexico. The catch was disposed of at sea.

The Gulf of Mexico Fishery Management Council has approved an 11-day red snapper season beginning June 1.