LATHROP — A 4-year-old boy and a 25-year-old adult are both believed to be drowning victims of the San Joaquin River Saturday afternoon at Dos Reis Park.

The two had been at a family gathering at about 4:45 p.m. when the youth fell into the river and the family member went into the water after him with both submerging and did not resurface, according to a Sheriff’s spokesman.

Search parties from the San Joaquin County Sheriff’s land and marine units combed the waters for several hours assisted by the Stockton Fire Department, the Lathrop-Manteca Fire Water Rescue units, the U.S. Coast Guard, a REACH helicopter and paramedics.  A search of the water and bank areas was conducted until 8:30 p.m. with negative results.

The Sheriff’s Boating Safety Unit resumed their search in the morning hours on Sunday.