TEHRAN, Iran (AP) — An explosion ripped through oil and gas pipelines at a pump house in Iran's southwest Tuesday, killing three oil workers and injuring four others, local media reported.

The blast struck the Einkhosh field some 500 kilometers (310 miles) southwest of the Iranian capital of Tehran, according to several news outlets, including the semiofficial Mehr agency. The condition of the injured workers was not immediately clear. A photo widely circulated from the scene showed a corpse under a blanket next to a charred building that apparently had served as a rest place for workers at the pump house.

The reports did not specify the cause of the explosion. Iranian Oil Minister Bijan Zanganeh ordered an investigation into the cause of the accident and sent his condolences to the families of the victims.

Such incidents are not uncommon in the country's aging oil and gas infrastructure, raising questions about worker safety at the sites. The facilities lack spare parts for repairs and suffer from poor maintenance as well as years of harsh American sanctions.

The sweltering summer heat, now exceeding 50 degrees Celsius (122 Fahrenheit) in some desert areas, has occasionally ignited fires at the sites.

Authorities said they would reroute oil from the affected field via pipelines to other facilities in oil-rich, southern Khuzestan province.

Last month, a petrochemical facility south of Tehran caught fire after temperatures in the city soared above 40 degrees Celsius (104 degrees Fahrenheit).

Bijan Zanganeh

Explosion kills 3 oil workers, injures more in south Iran