PENSACOLA, Fla. (AP) _ Shattered pieces of jet engine were gathered off an airport runway Sunday, remnants of shrapnel that shredded part of an airliner's fuselage and devastated a vacationing family.

Investigators had yet to determine why the left engine on a Delta Air Lines jet blew apart during takeoff, whether there was some internal problem or whether it sucked in a foreign object such as a bird, said George Black, a member of the National Transportation Safety Board.

Metal pieces flying from the engine, mounted on the side of the fuselage near the tail, ripped a gash about a foot wide and more than four feet long across the side of the plane, killing Anita Saxton, 39, her son Nolan, 12, and injuring two of her other children.

Mrs. Saxton, of Scottville, Mich., had been vacationing with three of her five children in the Pensacola area.

The two injured children were discharged from Sacred Heart Hospital on Sunday and joined with their father, Randy Saxton, who flew to Pensacola late Saturday.

Although dazed and burned, 15-year-old Derrick Saxton carried his sister, 9-year-old Spencer, from the plane after the pilot made an emergency stop on the runway, said their grandfather, William Saxton. Spencer had leg and facial injuries.

``Then he wanted to go back inside to get his mother and brother,'' said William Saxton, who said he spoke with Derrick by telephone soon after the accident from his home at Pentwater, Mich. ``He seems all right now, as much as he can be after this.''

Five of the other 142 passengers aboard the jetliner also were injured, but only one remained hospitalized Sunday, listed in serious condition after surgery for a broken leg. None of the five crew members was hurt.

Delta officials said Sunday there was no connection between the accident and deep cost-cutting that has pruned about 12,000 jobs from the Atlanta-based carrier since 1994.

NBC News reported Sunday that the very same engine involved in Saturday's accident had to be removed from a Delta plane in December after the cabin filled with smoke on a flight to Orlando.

The problem was traced to a leaky oil seal and was fixed while the engine was down for maintenance.

``We never had that problem again,'' Delta spokesman Dean Breest said. ``From the preliminary reports we have seen ... anyone who speculates that there's any correlation between the two (incidents) would be misleading at this point.''

Delta has had four engine-disabling incidents since April, according to NTSB records, The Tampa Tribune reported Sunday.

No one was hurt in any of those cases. Two of them involved MD-88 airliners, the same model involved in Saturday's accident.

In one of those engine accidents on June 22, a turbine blade punched a hole in the engine case and made a small hole in the engine's exterior metal covering.

While the cause of the latest engine failure is not yet known, Black explained what made it so lethal.

``Any engine has a lot of fairly massive parts rotating very rapidly,'' he said. ``It's just like slinging keys around on a chain. If something happens to that object it has to dissipate that energy. So it would be a violent event.''

The seven-member NTSB team was assisted by experts from Delta, the Federal Aviation Administration, plane manufacturer McDonnell Douglas and Pratt & Whitney, which made the two JT8D-219 engines that powered the MD-88 jetliner.

They were checking all of the plane's systems, maintenance records and its flight data and cockpit voice recorders, the so-called ``black boxes.'' They also were interviewing the pilot and co-pilot.

Black said experts would try to reconstruct the failed engine to find out what went wrong.

The runway where the accident happened could not be reopened until all the debris was removed, but airport operations continued uninterrupted on an alternate runway.

Also Saturday, another Pratt & Whitney engine failed, on TWA's Flight 114 from Seattle to St. Louis, prompting the pilot to land the MD-80 at Omaha, Neb. However, no debris escaped from that engine, a slightly less powerful model called the JT8D-217, Pratt & Whitney spokesman Mark Sullivan said Sunday.

The JT8D is one of the most common and reliable types of engines used on commercial aircraft, said Pratt & Whitney spokesman Mark Sullivan from the company's East Hartford, Conn., headquarters.

The engine powers 4,000 passenger and cargo jets. About a quarter of the engines are from the 200 series that was in the Delta plane.

This type of engine accident is ``very unusual _ catastrophic and unusual,'' said NTSB spokesman Michael Benson.

A similar failure involving a JT8D-9A engine, an earlier version of the type that failed here, penetrated the cabin of a ValuJet DC-9 preparing to take off from Atlanta on June 8, 1995. A flight attendant and six passengers were injured; a resulting fire destroyed the plane.

NTSB investigators found evidence that corrosion on a piece of that engine called a compressor disc had been plated over during a 1991 overhaul in Turkey. The agency then conducted special inspections of other engines that ValuJet had purchased from a Turkish airline.