Lawrence Reese said he had just entered his Lorton deli Wednesday morning when a powerful explosion rocked the shop on Richmond Highway.

“I remember walking into store, then I felt a blast,” Reese said. He was left with burns on his arms, stomach and face. The case has also generated a mystery.

Fairfax County police said a man was seen running from the Sub Shop shortly after the blast about 10:30 a.m. They say the cause of the explosion remains under investigation and Reese said he didn’t know what caused it.

“According to the preliminary investigation, there was some sort of incendiary event inside the business,” Broderick said. “There was obviously a fire explosion, but it’s too early to say whether it was an explosive device or something else.”

Reese said he had been unloading groceries from his vehicle in the parking lot before the blast occurred. He said he saw somebody at the scene, but did not know the person.

Police described the person leaving the area as a black man, but didn’t have additional details to identify him.

Flames from the blast engulfed the shop and it took firefighters about 10 minutes to douse the blaze, said Dan Schmidt, a Fairfax County fire department spokesman. The shop’s windows were knocked out.

A police helicopter and K9 units checked the scene Wednesday.

Police and Fairfax County fire marshals are jointly investigating the incident. The latter office will release the cause of the fire.

There was no estimate of the cost of the damage.