An explosion has rocked the Hoover Dam, after a transformer caught fire at the hydroelectric complex on the border between Nevada and Arizona.

Officials said there were no injuries following the fire on Tuesday in the turbine house of the massive power-generating dam, which supplies electricity to parts of three states. 

Water levels in Lake Mead, the reservoir created by the dam, are at historically low levels due to an ongoing mega-drought in the area, which was also experiencing extreme heat on Tuesday. 

It's unclear whether high demand for electricity, or diminished generating capacity due to low water levels, played a role in the fire. Officials said the cause of the fire was under investigation.

'There is no risk to the power grid and power is still being generated from the powerhouse,' said Jacklynn L. Gould, regional director for the federal Bureau of Reclamation, which operates the dam. 

Gould said that the Hoover Dam's A5 transformer caught fire at about 10am, and the blaze was extinguished within about 30 minutes by a fire brigade the Bureau maintains on-site. 

Video from the dam showed flames and smoke rising from a turbine house on the Arizona side of the Colorado River, at the foot of the 726-foot-tall dam, as terrified tourists were rushed to safety.

Massive explosion rocks Hoover Dam with black smoke and fire seen i...