Investigators looking into a fire that destroyed a warehouse at the Pine Bluff Arsenal are focusing on the cylindrical canisters that held white phosphorus inside the building, officials said Wednesday.

Some 7,500 of the canisters, along with the building, were destroyed in the June 6 fire.

"It could've been a leak, it could've been a weakness over time," said Arsenal Commander Col. Tom Woloszyn, standing in front of a sample of the canisters that burned in the fire after a news conference at the arsenal.

The green canisters stand 20 inches tall, are about 4 inches in diameter and have a black core.

He speculated that a seam in one or more of the canisters may have weakened over time and the phosphorus leaked out and caught fire.

Other causes for the fire, such as an electrical problem, have been ruled out, Woloszyn said.

The investigations won't be completed for another two or three weeks, he said.

An internal investigation board and an outside firm are trying to determine what caused the fire.

White phosphorus is used in ammunition and to generate smoke screens. The Pine Bluff Arsenal is the Army's sole producer of white phosphorus ammunition in the Western Hemisphere.

The fire was discovered by security guards shortly after midnight on June 6, a Monday. It was brought under control by 1 a.m. and had burned itself out by 5 p.m. before flaring up again around 1:30 p.m. Thursday. No one was injured in either incident.

White phosphorus is volatile and will catch fire when the temperature hits 90 degrees or higher, so firefighters are monitoring the scene around the clock and cooling the area with water.

The water is being collected and treated on site, said Larry Wright, senior civilian executive for the arsenal.

Occasional flare-ups are expected as the investigation wraps up and the cleanup begins, Woloszyn said. The cleanup should start in a month or so and will take two to three months, he said.

The warehouse, located near the arsenal's Warbritton Gate, was not part of the ongoing work to dispose of the arsenal's chemical weapons stockpile.

Prolonged exposure to the smoke can irritate the eyes, skin and nose. Results of air samples taken in the surrounding area showed high levels of particulates, but nothing that exceeded safety standards, Woloszyn said.

Anyone with prolonged symptoms from the smoke should seek medical attention, arsenal officials have said.

This story was published Friday, June 17, 2005.