Agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives gave the new details Wednesday afternoon, exactly one week after a fire broke at the Garden Ridge off the North Freeway near FM 242.
Officials with the Bureau of Alcohol, Tobacco, Firearms and Explosives say they examined a lot of evidence before coming to the conclusion.
"Between the forensic work that was completed and witness accounts, they were able to piece together the information that the fire was intentionally set," ATF assistant special agent Gary Orchowski said.
Authorities admitted having eyewitnesses come forward with information was a big help.
"We'd like to thank the public, as the public was of assistance in helping us follow up on numerous leads," Orchowski said.
No specific details were given, such as how or where the fire started. Authorities said the store did have surveillance video but wouldn't say if there is video of the fire.
The blaze was set somewhere in the middle of the store during business hours last Wednesday. The blaze quickly grew to three-alarms and about 110,000 square feet were damaged, costing an estimated $15 million .
Between two and three dozen customers, along with 23 employees, were inside the store at the time but everyone got out safely. There was only one minor injury -- a case of smoke inhalation due to the fire.
Conroe authorities also talked about why they requested help from federal authorities.
"In a large building like this, just the sheer size and length of the investigation is very manpower intensive; it's a lot for a local agency so a national response is available upon request," Conroe Deputy Fire Marshal Joe Craig said.
Authorities wouldn't say if there are more than one suspect in this fire, but did say there is the possibility of federal charges.
"A business has to be involved in more than one state; state lines have to have been crossed," Orchowski said.
ATF officials say they're working with the Montgomery County District Attorney's Office if/when charges will be filed.
So far, no arrests have yet been made.