JUBA, South Sudan — At least 18 people were killed when a small plane crashed in South Sudan’s Unity State on Monday, according to local radio station Miraya, which is operated by the United Nations Mission in South Sudan (UNMISS).

The aircraft, carrying 21 passengers and crew, was taking off from an oil field in Unity State when it went down. The cause of the crash remains unknown.

The latest incident highlights the precarious state of aviation safety in South Sudan, which has been plagued by conflict for years. In September 2018, a small plane carrying at least 19 people crashed while en route from the capital, Juba, to the town of Paloich. In 2015, a Russian-made cargo plane crashed shortly after takeoff from Juba International Airport, killing dozens of people.