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.

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

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

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