TENNGA, Ga. (AP) _ A train slammed into a school bus this morning at an ungated crossing near the Georgia-Tennessee line, splitting it in two and killing two children. The five other elementary school pupils on board were critically injured.

No one on the CSX freight train was injured.

The Murray County school bus was picking up children to go to Northwest Elementary School north of Chatsworth. The bus had crossed into Polk County, Tenn., to turn around when it was struck by the train at about 6:30 a.m.

The 72-passenger bus was on the early part of its regular route and had more pickups to go, officials said.

The collision ``sounded like damn thunder or a bomb blown up,'' said Joe Brown, who lives about 300 feet away and helped rescue the victims.

The bus split, with the cab portion driven about 100 yards along the track and the frame pushed 30 yards. Some of the wreckage ended up across the state line in Georgia, said Dana Keeton of the Tennessee Highway Patrol.

Some of the children were ejected from the bus, Brown said. One of the two children killed was his niece, he said.

There is a sign but no signal lights or bars at the crossing. The track curves through pine trees in hilly terrain, making it difficult for a train's crew to see the crossing, Brown said. He said the weather was mostly clear.

The train's engineer told investigators he blew his whistle as he approached the intersection and applied his emergency brake as soon as he saw the bus, said Tennessee state Trooper Ken Uselton.

Five children, ages 5 to 9, were admitted in critical condition at Erlanger Medical Center in Chattanooga, spokeswoman Sharon Kayhill said. Two were later upgraded to serious condition, she said.

The bus driver was in stable condition at Murray County Medical Center in Chatsworth. She has worked two years as a substitute and one year as a full-time driver, said Kate Pannell, personnel director for Murray County schools. She knew of no accidents on the driver's record.

The bus usually goes 100 feet into Tennessee to turn around in a church parking lot, said Veronica Ownby, who lives about a quarter of a mile from the crossing.

Her grandson, 7-year-old Zachary Matthews, rides the bus in the afternoons but she drives him to school in the mornings, she said. ``He didn't go this morning,'' she said. ``He's upset over all his little buddies.''

Northwest Elementary maintained its regular schedule today. Three counselors were at the school, although most children were not told of the accident, school secretary Tommie Brown said.

``We feel like that's best for the children, just having a regular day of classes,'' she said.

Kathy Burns, a spokeswoman for CSX, said the train was bound from Cincinnati to Tampa, Fla.

Murray County, with about 31,000 people, is a blue-collar manufacturing area dependent on carpet mills in nearby Dalton.