Explosion, fire erupt at MarkWest natural gas processing facility in Houston, Penn.

An explosion started a fire at a natural gas processing plant about 40 kilometres south of Pittsburgh on Thursday, reports said.

The facility run by MarkWest Energy Partners experienced a blast that had dispatchers sending first responders to the scene in Houston, Penn. at just after 6 p.m. ET, KDKA-TV reported.

The incident unfolded close to two temporary tanks that were located on site for routine maintenance, according to a statement from Marathon Petroleum Corp.

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This resulted in a fire, the statement said.

WATCH: Emergency crews were on scene following an explosion at the MarkWest Energy gas plant in Pennsylvania on Thursday evening

1:28 Aerial video of MarkWest Energy plant following explosion

Four people were hurt and taken to hospital.

The fire was later put out and the plant was shut down. There were no off-site effects, according to Marathon.

The cause of the fire is still being investigated.