Authorities say 20-year-old Joe Le of Anaheim lost his footing and was swept away in the strong current while crossing the San Gabriel River near the Camp Williams Resort.
Air search teams and swiftwater rescue crews have been looking for Le ever since.
The L.A. Co. Sheriff Deputy Gordon PIO and San Dimas Sheriff watch commander
The body of a male Asian, 21 to 22 years of age, was found at East Fork Rd. in Coyote Flats near Azusa Canyon late Sunday afternoon. The body was not identified.
Rescuers say the situation is not looking good, but his sister is not giving up.
"I'm going to continue to look for him until I find him. My brother is very smart, very clever and I'm still hoping, until I find him," said his sister, Victoria Le, who has organized her own search group using Facebook.
Authorities found Le's backpack.
Search teams kept looking for Le until about 10 p.m. Sunday and were slate to resume their search Monday if Le is not found.
