PHILADELPHIA (CBS) – Police in Camden say they’ve increased patrols in the city’s industrial areas in the wake of two serious fires in vacant factory buildings.

Authorities say more cops are on duty as a “proactive step” — as neighbors express concerns that the blazes are the work of an arsonist.

Officials have not released a cause for either fire. Local investigators are working with federal officials to determine how they started and if the two are connected.

First came Thursday’s 12-alarmer in the city’s Parkside neighborhood. Then, early Saturday, fire broke out at an old brick garment factory at Broadway and Winslow. It went to eight alarms before it was brought under control.

Camden Fire Chief Michael Harper says both blazes are under investigation.

“Our Fire Marshall’s office, in coordination with the ATF agency, they’re already doing a lot of investigative work to determine a cause and origin, see if there’s any correlation between the two fires.”

But Stephanie Culbreath, who lives across the street, says she has no doubt about the cause. “In my heart I know it was set. I really believe it was arson.”

Reported By Molly Daly, KYW Newsradio