PORT VUE, Penn. -- Allegheny County authorities are conducting an active river rescue search for a 13-year-old boy in the Youghiogheny River after he disappeared while swimming.

Emergency responders were searching for the boy at about 8 p.m. Sunday night near Birdie's Landing on River Road in Port Vue, Penn., an emergency dispatcher said.

The boy was last seen wearing an orange shirt and blue shorts.

The dispatcher said the boy had been swimming in the river with an 11-year-old girl. She came out of the river, but he did not.

A state police helicopter was sent to aid in the search.

WTAE-TV was told that the search is moving upriver toward Versailles.