GASTON, Ore. » It was supposed to be a pleasant lakeside picnic for a 42-year-old mother, her 25-year-old daughter, teenage son and 3-year-old grandson.

But for reasons that are still unclear it turned into a tragedy. All four family members were found drowned at Henry Hagg Lake, a popular reservoir 25 miles west of Portland.

Divers on Tuesday recovered three of the bodies near a picnic area — the day after lake goers found the 3-year-old boy face-down in the water and unconscious, near the same spot. They and emergency officials performed CPR, but the boy died at the scene.

No one saw what happened on Monday. Law enforcement officials said they found no sign of foul play.

"We’re just considering this a tragic accident," said Sgt. Bob Ray of the Washington County sheriff’s office.

Deputies identified the three bodies found Tuesday as those of Jova Ixtacua-Castano, 42, her daughter Gabriela Garcia-Ixtacua, 25, and son Michael Garcia-Ixtacua, 13.

The 3-year-old boy was identified as Jeremy Scholl, the son of Gabriela Garcia-Ixtacua. The family lived in nearby Hillsboro.

Authorities said the side of Henry Hagg Lake where the four family members were found is heavily used by swimmers and has been the site of numerous other drownings and near drownings.

The area is dangerous because of a steep underwater drop-off formed by the channel of a former river bed that runs into the reservoir, and due to a muddy, slippery bottom.

The drop-off is especially treacherous toward the end of summer, when the water level gets low, said the fire chief of nearby Gaston, Roger Mesenbrink, who has responded to multiple drownings at that spot.

"The channel becomes deceiving because it looks like it’s not deep, and it isn’t when you first walk in. But then it abruptly drops off, and you go from 2 feet to 10 feet of water in a second," Mesenbrink said. "If you slip off that edge, you’ll take a gulp of water and it’s hard to make it back unless you’re a strong swimmer."

In 2012, eight children nearly drowned after wading into the lake and stepping from that underwater drop-off. They were saved by six people at a family reunion who heard the children yelling and formed a human chain to pull them to shore.

In 2008, a 27-year-old Portland man drowned at the same spot while trying to swim across the channel.

Because of its size of nearly 2 square miles, the lake has no lifeguards, but the sheriff’s office uses a vessel on weekends for patrols.

A life jacket kiosk was installed at the picnic area after the 2008 drowning, but the four family members on Monday didn’t use life jackets — despite the fact that relatives told investigators the four did not know how to swim, Mesenbrink said.

The three bodies were discovered about 40 feet offshore in 8 feet of water, and about 50 yards from the spot where the 3-year-old was found near the shoreline.

Authorities worried about the rest of the family after they recovered the boy’s body and found personal items nearby, including a beach towel, cooler, shoes, identification, as well as a small dog on a leash.

They also discovered that a vehicle left at the parking lot near the lake was owned by a family member whose identification was found at the lake’s shore.

The lake — created 40 years ago by a dam project — is a busy recreation site for boaters, fishermen and swimmers, drawing 800,000 visitors a year — 6,000 a day on busy summer weekends, officials said. It also provides irrigation water for area farms, drinking water for Portland suburbs, and additional flows for the Tualatin River.

Washington County, which maintains and operates the lake, declined to comment about whether the county has ever considered closing off to swimmers the area where all the drownings and near-drownings have occurred.

"Washington County takes safety seriously with respect to public use of Hagg Lake and Scoggins Valley Park," spokesman Philip Bransford said in a statement. "We work closely with the Washington County Sheriff’s Office, Gaston Rural Fire District and Hillsboro Fire & Rescue to promote safe practices on Hagg Lake, including the free use of life vests stationed on the banks of the lake."