A recent trend of fires breaking out in vacant buildings across the city is troubling San Antonio firefighters and residents.

One of the most recent such fires broke out after 4 a.m. Thursday inside what was supposed to be an unoccupied home, KSAT reported.

Firefighters had been to the same house on Saturday, Battalion Chief Oscar Gonzalez said. 

“We had a vacant house that was fully engulfed in flames. At this point, we’re kind of following a couple of leads."

Gonzalez said the cause remains under investigation.

Firefighters urge people to report suspicious activity.