CHELAN, Wash. (AP) _ As their three children slept during the ride back from a Fourth of July fireworks show, David and Jennifer Hoffpauir stopped their van at a park for a quick bathroom break.

When they came back, the van was gone. It had rolled into the Columbia River, and the children drowned.

``At that moment, they panicked,'' Sheriff Dan LaRoche. ``They could see where it had rolled into the river.''

The van flipped upside down and sank in the swift current. Hoffpauir jumped in and tried in vain to open the locked doors, LaRoche said. By the time workers could finally attach a cable to the van, break a window and pull the children out, they had been under the chilly water for more than two hours.

A team of nearly a dozen doctors and nurses at Lake Chelan Community Hospital then spent three hours trying to revive the children.

LaRoche said the automatic-transmission van was in reverse when it was pulled from the water, and he was looking into the possibility it had been left in park and slipped into gear.

Investigators examined the vehicle Wednesday afternoon and found the automatic transmission did not lock properly, LaRoche said. The key can be removed while the van is still in gear, and the gears can be changed even when the key isn't in the ignition, he said.

The Hoffpauir's Aerostar was a 1990 model. In 1991, Ford warned 780,000 owners of 1991 Aerostars Explorers and 1990 Aerostar and Rangers of a potential problem with the automatic transmission.

The company said at the time that when shifted into park, the transmission may not hold the vehicle.

Ford spokeswoman Francine Romine in Detroit said Wednesday she could not comment until she had checked company records on the vehicles.

``It's just a tragedy,'' said the youngsters' grandfather, Kenneth Hoffpauir. ``I tell myself these things happen, I suppose, even if it's hard to understand why. The Lord knows what he's doing.''

The Hoffpauirs, who teach at the Seventh-Day Adventist school in the town of Omak, were making the 50-mile return trip from the fireworks display at Lake Chelan.

It was shortly before midnight when the parents stopped to use restrooms at Beebe Bridge Park and left the children locked inside. The van sank quickly in the 15 to 20 feet of water, LaRoche said.

Dead were 9-month-old Nathon; Brian 6; and Ashley, 8. The coroner said autopsies confirmed drowning.

``They were just good kids, you know, just an all-around good family,'' said fellow church member Michael Nearents. ``You don't expect something like that, and when it happens, it floors you.''