LONDON -- Four people were killed when a plane crashed at London Southend Airport on Sunday, Essex police confirmed on Monday.

Morgan Cronin, chief superintendent of Essex County, confirmed all four passengers were killed in the plane crash, and were believed to be foreign nationals. Efforts are ongoing to confirm their identities.

A "significant air exclusion zone" has been put in place surrounding the crash site, Cronin said.

Lisa Fitzsimons, lead investigator at the Air Accidents Investigation Branch (AAIB), identified the aircraft involved as a Beech B200 Super King Air. The AAIB has launched a safety investigation to determine the circumstances and cause of the tragic incident.

According to local media reports, the victims included three men and one woman.

Video footage captured a massive fireball following the crash, while images posted online showed intense flames and thick black smoke billowing from the wreckage on Sunday afternoon.

Essex Police said officers responded to "reports of a collision involving a 12-meter aircraft" shortly before 4 pm local time (1500 GMT).

The aircraft was operated by Dutch firm Zeusch Aviation. It was due to fly to Lelystad Airport in the Netherlands.

Zeusch Aviation confirmed its SUZ1 flight had been "involved in an accident" at the London airport and said its thoughts were with "everyone who has been affected."

Southend Airport said it would remain closed until further notice due to the "serious incident".