NEW YORK, Aug. 4 -- Horsehead Holding Corp (ZINC.O: Quote) said Tuesday a declaration of force majeure on some zinc oxide and special high-grade zinc contracts may last for several months following an explosion at the company's zinc refining facility in Monaca, Pennsylvania, on July 22.

"It is anticipated that it could take several months for production capabilities at the refinery to be fully restored," said a company spokesperson.

The refinery explosion resulted in the death of two employees.

The zinc refinery remains on temporary shutdown pending completion of an investigation and assessment of the damage.

"We are expecting it to be a couple of months, but that will be keyed off of the investigation," the spokesperson said.

Teams from the U.S. Occupational, Safety and Health Administration (OSHA) and the U.S. Chemical Safety & Hazard Investigation Board (CSB) are investigating the cause and the circumstances of the blast, according to a company press release dated July 28.

A preliminary assessment of the damage indicates that each of the 10 columns used to produce zinc oxide and refined zinc metal in the refining facility will need to be rebuilt before production can be safely restarted using these columns.

"The one (column) that suffered the explosion will certainly have to be reconstructed," the spokesperson added.

"The others will have to be rebuilt ... what that means is rebricking the inside and putting in new trays," he said.

While still active, the smelting facility and other operations at the plant are at reduced rates. The Monaca plant is the country's largest zinc smelter, according to the company's website.

The cost of repairs and the loss of revenue from its zinc oxide sales during the rebuilding period -- historically representing 40 percent of the company's revenues -- is expected to be partially offset by increased metal sales and will be subject to recovery under the company's business interruption and property insurance, the press release said.