An airplane cleaner at Istanbul's Sabiha Gokcen airport has died of injuries suffered Wednesday in an explosion near a parked aircraft, a Turkish news agency said.

The cause of the blast, which also injured a second cleaner, was not clear.

The private Dogan news agency reported the death of the female cleaner.

Pegasus Airlines, a Turkish carrier, said the blast occurred at 2:05 a.m. Wednesday (7:05 p.m. EST Tuesday) when no passengers were aboard the plane.

Turkey's state-run Anadolu Agency said police armed with rifles and wearing protective vests imposed tight security at entrances to the airport after the blast, searching vehicles in the area.

The airport operator says the cause of the explosion is under investigation.