Investigators plan to return on Tuesday to the scene of an explosion at a Rockmart feed mill that killed one man and injured five other people, the spokesman for state Insurance and Fire Commissioner Ralph Hudgens' office said.

Before investigators can enter JCG Farms feed mill, structural engineers must figure out how to go in first, which is a normal protocol for large facilities, Glenn Allen said.

“The investigation will not continue today,” he told The Atlanta Journal-Constitution on Monday. “It will continue tomorrow.”

Justin Deems, 25, was killed in the Sunday blast, which shook JCG Farms and nearby properties off Ga. 101. Of the five injured, four were taken to hospitals in Rome and Marietta. Another person was flown to Grady Memorial Hospital in Atlanta in critical condition and remained there on Monday, according to Channel 2 Action News.

The Bureau of Alcohol, Tobacco, Firearms and Explosives was called in Sunday to investigate because they have expertise in large commercial structures, Special Agent Will Creech said. Local and state fire investigators are assisting them, and the Occupational Safety and Health Administration was notified.

Firefighters uncovered a gas leak at the site of the explosion, but investigators do not know whether it caused the blast or resulted from it, Rockmart Fire and Emergency Services Chief Todd Queen said Sunday. All utilities at the site were shut off.

The explosion caused the partial collapse of a low-rise building next to the plant’s 100-foot tall storage and processing facility, which is about 50 miles northwest of Atlanta, Queen said. Ga. 101 remained closed late Sunday as engineers assessed the structural damage.

Eight people were working at the mill, which processes chicken feed for farms in the region, Queen said.

A much smaller dust explosion took place at the plant in recent years but in a different building, Queen said. An OSHA online inspections database lists two complaints in August 2013, but gives few details.

“It was nowhere near the magnitude of what was experienced today,” Queen said Sunday.

Justin Deems' mother,Deems, said Sunday's blast was so powerful it pushed her son out of a second-story window. Later, family members told her they could hear the explosion 10 miles away.

Deems is survived by wife , brothers Jason, 24, and Travis, 23; sisters Ashley, 21, and Hope, 18, and 10 half brothers and sisters.

The Deems family is asking for donations to help cover funeral costs.