DALLAS (CBSDFW.COM) — Dallas fire officials and Oncor are investigating after flames and smoke were seen rising from multiple manhole covers Sunday morning.

Just before 6:30 a.m. Sept. 1, Dallas Fire-Rescue units were sent to a call for reports of flames shooting up from manhole covers on the 1200 block of Elm Street in Downtown Dallas.

When firefighters arrived, they saw smoke coming from the manhole covers, which led to underground vaults where electrical transformers were located.

By the time firefighters got there, there were little flames left and the fire was extinguished in about an hour.

No injuries were reported, and this remains an ongoing investigation.