An investigation was underway after San Bernardino firefighters responded to seven fires — all deemed “suspicious” in nature — in the city over a 24-hour period, authorities said early Wednesday.

The latest fire was reported at a residence in the 1000 block of Stoddard Avenue at about 12 a.m., according to the San Bernardino Fire Department.

The burning structure was fully engulfed in flames when first responders arrived at the scene, prompting firefighters to mount a defensive attack in order to protect surrounding homes, a tweet from the department stated.

It took firefighters roughly 30 minutes to extinguish the blaze, which did not spread to any neighboring buildings, fire officials said. However, the residence was declared a total loss.

No injuries to civilians or firefighters have been reported.

Although the cause of the blaze remained under investigation, it appeared to be suspicious in nature, according to authorities.

It was not immediately known if any of the fires were connected, investigators said.

No further information was immediately available.

KTLA’s Alberto Mendez contributed to this story.