ATCHISON, KANSAS, U.S. — Three people are still missing following an Oct. 29 explosion at the Bartlett Grain Co. grain elevator in Atchison, Kansas, U.S. Three others were killed in the explosion and two were critically injured.

The facility was too unstable to continue the search on Oct. 30 for the missing men, the Kansas City Star reported. The search, which has shifted to a recovery operations, was resuming on the morning of Oct. 31.

The missing include one Bartlett employee and two grain inspectors. The three confirmed dead were identified as Bartlett Grain workers John Burke, 24; Ryan Federinko, 21; and Chad Roberts, 20. Four other people present during the explosion were not injured, the newspaper reported.

The explosion blew the head house off the top of the elevator and blasted a hole in the side of the concrete structure, theKansas City Starreported. Parts of the head house were hanging from the top of the elevator and officials were worried it would fall.

Cause of the explosion, which happened while workers were loading a train with corn, was not immediately known, said Bartlett Grain President Bill Fellows.

An inspector from the Occupational Safety and Health Administration was at the site on Oct. 30. and a Kansas Highway Patrol helicopter circled over the facility with a structural engineer hired by Bartlett.