BEAUMONT, Texas (AP) _ Divers swam in a zigzag in the murky Neches River on Monday to search for four people reported missing after two pleasure boats collided, and authorities said they suspected speed and alcohol played a role in the accident.

Seven other people remained hospitalized in stable condition from injuries suffered Sunday night in the collision near the Bethlehem Shipyard, in a bend in the river's main channel, authorities said.

A dry dock at the shipyard was searched late Sunday by Fire Department divers for the missing, identified as two men and two women. The divers resumed the search about mid-morning, said Fire Department spokesman Tommy May.

Divers swam in systematic, zigzags through the roughly 40-foot deep area near where the accident occurred, May said. Underwater visibility was near zero, he said.

Meanwhile, the Jefferson County Sheriff's Department interviewed witnesses, said Chief Deputy Cal Blanchard.

''Obviously, one of the boats appeared to be overloaded, speed will be an issue in that the combined speeds would have been approaching 70 mph,'' said Blanchard.

''It is apparent alcohol is going to be involved to some extent, right now we don't know to what extent,'' he said.

Ten people were in one boat, a 17-foot outboard, and six were in the other boat, which appeared to be about 18 feet long, according to Beaumont Fire Chief Pete Shelton.

Although Shelton said there were 16 people aboard the two boats, only 15 people were listed as either hospitalized, treated and released, missing or not injured.

The four people missing all were occupants of the 17-foot boat.

Eight people were taken to Baptist Hospital after the accident. Two were treated and released, while six remained in stable condition Monday. Two people were taken to St. Elizabeth Hospital. One was released; the other was in stable condition Monday.

Kyle Wheelus, commander of the local auxiliary of the U.S. Coast Guard, said the auxiliary and the Orange County Sheriff's Office were pulling their boats from the water after being on patrol during a raft race when they learned of the accident.

When they arrived at the scene they found one boat under tow and the other turned over with the propeller sticking in the air, Wheelus said.

A woman was wedged under seats in the front of the upright boat and a man was pinned in the back of the boat, he said. Three more people were in the water, Wheelus said.

''We started gathering all the blankets we could, trying to keep the people warm,'' Wheelus said.