Federal investigators Friday marked and mapped a schoolyard where flaming debris of two aircraft landed from a collision that killed U.S. Sen. John Heinz III and six others, including two children on the ground.

The twin-engine plane carrying Heinz, R-Pa., from a news conference in Williamsport collided with a helicopter above Merion Elementary School just after noon Thursday. The plane had reported landing gear trouble shortly before the collision.Heinz, his plane's two pilots, the two helicopter pilots and two elementary school students on the ground were killed. A shower of debris rained down on the campus and the adjacent neighborhood of old stone houses and manicured lawns. One child was hospitalized with serious burns. Two other children and two school employees suffered minor burns.

"The people of Pennsylvania have lost a great leader and the nation has lost a great senator," President Bush said in a statement from California.

Utah's two senators both expressed anguish over the death of Heinz.

Sen. Jake Garn, R-Utah, said "I am deeply saddened over the death of my dear friend and colleague. John and I served together on the Senate Banking Committee for 15 years. I will miss him tremendously. He was an outstanding senator and a man of the highest character and honor."

Garn added that he and Heinz skiied together at the Senators Ski Cup in Utah and enjoyed many happy times together.

Sen. Orrin Hatch, R-Utah, called Heinz one of the great experts in the Senate on banking and financial legislation.

"He mastered the very complex subject of international trade," Hatch noted. He was a great senator, and one I will miss very much."

Heinz was heir to the Heinz food empire, making him one of the nation's wealthiest politicians.

Susan Coughlin, vice chairwoman of the National Transportation Safety Board, arrived on the scene Thursday and spoke to reporters as firefighters were plucking a red scarf and other debris out of a tree.

"We will be conducting this as a major accident investigation with a full team on board," she said.

Heinz, 52, was the second-ranking Republican on the Senate Banking, Housing and Urban Affairs Committee and the ranking GOP member of Banking's securities subcommittee.

First elected to the U.S. Senate in 1976, he was re-elected in 1982 and 1988.

He was the largest individual shareholder of H.J. Heinz Co., the international food company founded in 1869 by his great-grandfather.

His death threw Pennsylvania Republican politics into turmoil. State Auditor General Barbara Hafer, a Republican, said party officials were discussing a possible successor.

"There were a lot of calls back and forth" she said, but declined to discuss those named.