As one business displaced by a Thursday morning fire reopened on Monday, and as another made plans to do so, the cause of that four-alarm blaze remained unknown.

The fire, which completely destroyed the medical complex that housed the medical practice of Dr. Bruce Coffey and his sons, began around 3 a.m. Thursday morning. A massive response from Scott County’s volunteer fire departments persisted throughout the morning, and some firefighters remained on the scene through much of the day on Thursday.

Exactly how the fire started remained unknown as of Monday morning, as a Tennessee Bureau of Investigation probe continued. Darryl Laxton, Oneida’s chief of police, said that his officers assisted the investigation by “sitting on” the scene throughout the day on Thursday and the following night as TBI prepared to conduct a review of the scene with special equipment that can detect the source of fires.

Laxton said that such investigations by the TBI are not uncommon, as fire investigations that were once under the purview of the state fire marshal’s office are now handled by the state’s top law enforcement agency.

Contrary to popular rumor, Laxton said an explosion inside the building was not the source of the blaze.

“It’s like the firefighters said: the only thing exploding were the oxygen tanks,” Laxton said.

The chief’s comments echoed those of one of his officers who was on the scene Thursday morning, who previously told the Independent Herald that the fire started like any other before it became so hot that the oxygen tanks began exploding.

No one was inside the business at the time of the blaze, and no injuries were reported.

According to sources at the scene, among the first to arrive besides fires responders was pharmacist Mark Byrd, an Oneida alderman who owns Mark’s Family Pharmacy, one of four businesses destroyed by the blaze. Byrd then awoke Coffey, who rushed to the scene.

Related: Court documents unveil extent of feds’ case against Dr. Bruce Coffey

In all, there were four businesses housed at the facility, and all were destroyed.

Mark’s Family Pharmacy had reopened by Monday morning, following a whirlwind effort to temporarily relocate to Main Street.

The pharmacy’s temporary location is 280 South Main Street, behind Main Cell Repairs and Young’s Jewelry. Byrd’s wife, Trina Byrd, said in a Facebook post on Thursday that she and her husband “have been overwhelmed with calls, messages, even snap chats from our friends of this community.”

Doctors Coffey also said that it would reopen, though no specifics were given.

“Our priority is our patients. We have staff that will be answering calls and helping coordinate care. We are going to be opening back up and will release a location and start date soon,” the clinic said in a Facebook post on Saturday.

Nick Botts, a manager of Buckeye Home Medical Equipment in Scott County, said the company does not currently have plans to reopen its Oneida office. Buckeye’s primary Scott County location has long been in Huntsville; however, a second location opened in Oneida, originally at the Omedco building on Main Street. Last summer, following First National Bank’s purchase of the Omedco property and its planned razing, Buckeye moved to the Coffey building on Underpass Drive.

A request from the IH to PT Solutions’ corporate offices regarding plans to reopen in Oneida was not immediately answered.