The catastrophe began with a dull, sickening noise. Paul Jones, a Texas A&M University freshman, was about halfway up the bonfire pile, 20 feet from the ground, when he heard it.

"It was a real low-toned, thunderous pop," he recalled today. Above and below him on the immense, neatly stacked pile of about 4,000 heavy logs, dozens of his fellow students were at work early Thursday, hoisting and tying tree trunks and branches in the most revered tradition of Texas A&M. The six-tiered pile of wood, intended to reach 55 feet into the East Texas sky when complete, was to have been set ablaze next week at an annual football rally, the 89th bonfire celebration here in 90 years.

"It was a breaking sound," said Jones, 19, standing this afternoon on the campus polo field where tragedy visited at 2:28 a.m. (CST) Thursday. It was the ungodly sound of the pile, then 40 feet high, beginning to fall. Within seconds, in a crush of hundreds of tons of wood, 12 people--including six freshmen, four sophomores, one senior and an A&M graduate--lay dead or dying, some of them buried. The cause of the collapse remained a mystery tonight after the 12th victim died at a hospital today, and the grieving university prepared for what it said will be an exhaustive investigation.

"Then it leaned," Jones said of the pile. "And every kind of noise you could imagine started: wood breaking, cracking, splitting. I heard screams and hollering. And that's when it just came down, quick. It didn't stop or slow or anything."

The noise could be heard a quarter-mile away on the 5,200-acre campus, Texas's second-biggest university, 80 miles east of Austin.

"I just kind of stood my ground and rode it down," Jones said. "When I hit, I got tossed around a couple of times. People were yelling and crying. I ended up landing on some logs. And logs fell across my back and the back of my legs."

"Bonfire," they call it here--just "Bonfire," one word, capitalized, like "Christmas" or "Thanksgiving." It's a yearly festival of A&M pride and the culmination of a month of hard labor and engineering work. The pile is set ablaze before the Aggies' annual Thanksgiving weekend football showdown with the arch-rival Longhorns of the University of Texas at Austin, the only bigger school in the state.

As at least six victims of the disaster remained hospitalized today, at least two of them in critical condition, hundreds of mourners stood on the perimeter of field under a cloudy sky. They brought flowers and notes of remembrance of the dead. They knelt and prayed by a temporary fence surrounding the field, where workers had set the logs in dozens of small, neat piles.

The 43,500-student campus is "brokenhearted," A&M President Ray Bowen said.

The university said experts from its colleges of engineering and architecture, as well as outside consultants, would work to determine the cause of the collapse in an investigation that could last months.

The bonfire tradition, canceled for next week, began in 1909 and was observed every year except 1963, after the assassination in Dallas of President John F. Kennedy. Students, some experienced and others newly trained, cut thousands of logs starting in October. After the wood is hauled to the campus, the students, working round-the-clock in shifts, erect the massive bonfire stack, with help from engineers, heavy equipment operators and other experts, the university said.

The logs, about 7,000 of them by the time the job is done, are stacked in the shape of a tiered wedding cake around a center pole--actually two poles fastened end to end with notches, glue, bolts, wire and steel plates. The pole is secured about 10 feet in the ground. Some witnesses, including Jones, said the center pole may have snapped, causing the logs to crash down. But Texas A&M spokesman Lane Stephenson said investigators are not sure whether the pole broke before or during the collapse.

Rusty Thompson, an A&M staff member and adviser on the project, said the design of the structure "evolved" in the tradition's early years but has not changed since 1947. He said 50 to 70 students, a number consistent with previous years, were on the stack when it fell.

"Safety first is something we always talk about here, just like a construction company would talk about it," he said.

One of the questions confronting the school is whether to carry on the tradition next year. A group calling itself Aggies Against Bonfire has campaigned against it in the past, saying the bonfire is a waste of resources and attracts too many drunken revelers. More than 50,000 people attend the annual event. But mourners at the field today, as well as several university officials, said the mood on campus favors keeping the tradition.

What began in 1909 as "just a burning desire to beat the University of Texas" has "developed over the years into more than that," said Thompson. "It's about friendship, unity, people coming together to work on a common project and accomplish a goal."

Paul Jones, from a small East Texas town, came to A&M this year partly because of the many traditions the 123-year-old former all-male military school takes seriously, including Bonfire. He was quick to volunteer for the project and was binding two logs with a length of metal wire when he heard that first noise. Now he stood by the field with a bandage on his forehead, another on his right hand, and palm-size bruises on his back and legs.

"I brought flowers out here," he said. "And I was just going to do a little praying, say farewell to some Aggies who didn't make it."

How a Tradition Is Built

Almost a century of tradition and history make up the Aggie bonfire. Nearly 7,000 trees are donated by area landowners; 5,000 students and other workers typically spend a total of 125,000 work hours per year building the structure. Since 1970, its height has been limited to 55 feet. Before that, it towered over 100 feet. The Aggies have built their bonfire since 1947 using this spliced-centerpole technique:

Center Pole

The center pole is two telephone poles lap-jointed together, joined with 5 gallons of glue, 8 steel bolts and plates and 3/8" steel cable.

More steel cable is then wrapped around the joint and secured by 11/2" steel staples. The center pole sits in a 10-foot hole in the ground.

Cross beams and other poles make up the interior framework.

Top Cap

The steel top cap is the attachment point for two `tag lines` that go through pulleys. These lines are used to raise the timbers into place. Guy wires also are attached and fastened to four light towers below.

Workers are suspended from ropes that are connected to as many as 50 carabiners at the top of the pole.

When the stack is finished, the top cap and carabiner assembly are sawed off, and the parts saved for the following year.

Erecting the Structure

An engineer called the "scarecrow" directs a ground crew known as the `tag line` team. They steady the line as a truck, using a pulley system, backs up, hoisting a 10-foot log to the desired level. Once in place, the logs are secured together in groups of three, using baling wire.

The structure is designed to twist inward and collapse on itself as it burns.

SOURCES: The Dallas Morning News via Associated Press