A health official in Azerbaijan says at least 20 people have been injured in an explosion at a defense plant.

There was no immediate indication of the cause of the Tuesday afternoon blast at the plant in Shirvan, 100 kilometers (60 miles) southwest of the capital, Baku.

A spokeswoman for the national health ministry, Lia Bairamova, said the 20 people have been taken to a local hospital with various injuries. She did not elaborate.

The plant is managed by the Defense Industry Ministry, but its exact products are not stated on the ministry's website.

Azerbaijan is an oil-rich nation on the Caspian Sea.