The Army Corps of Engineers is investigating work done by contractors - including an Alpine firm - prior to a natural gas explosion at Fort Benjamin Harrison last December.

An Army report, released under the Freedom of Information Act to The Indianapolis News, recommended that criminal investigators determine whether two construction firms, Ibex Ltd. of Alpine, Utah, and Roessler Construction Co. of Rantoul, Ill., complied with Army Corps of Engineers contract specifications, The News reported Wednesday.The investigating officer, Lt. Col. Donald G. Peters, noted that several gas leaks were reported by residents following two-phase renovations of Harrison Village in 1987. His report said most of the actual leaks were due to the failure of a fusion joint installed by Ibex.

Col. Robert W. Sweeney, the base chief of staff, said Army officials turned down a recommendation for an investigation by the Army's Criminal Investigation Division. Instead, the Corps of Engineers will review the firms' work.

The report criticized the Corps of Engineers for not specifying how abandoned gas lines should be handled.

The Army announced on March 27 that the explosion probably was caused when gas seeped from an uncapped pipeline under a four-unit apartment building at 1025 Drumn Drive.

Ibex President Ben Shippen declined comment. Lawrence W. Roessler of Roessler Construction said his company met the terms of its contract.

"We will welcome and will fully cooperate with a further investigation by the Army Corps of Engineers," he said.

Two people died from the Dec. 9 explosion. Jannae Encarnacion, 5, died of smoke inhalation and burns soon after the fire broke out. Sgt. Stoney Bell, 35, died April 3 at Brooke Army Medical Center in San Antonio, Texas.