An explosion at Istanbul's second-largest airport on Wednesday killed one cleaner on an airplane and injured another, Dogan news agency said, adding authorities were investigating whether the blast was caused by a bomb, Reuters reported.

Budget carrier Pegasus said the explosion at Sabiha Gokcen airport on the Asian side of the city occurred at 2:05 a.m. (0005 GMT), when no passengers were in the area. It said its operations at the airport were continuing normally.

Police armed with rifles and protective vests imposed tight security at entrances to the airport after the blast, searching vehicles while a police helicopter circled overhead, state-run Anadolu Agency said.

Anadolu earlier reported that one of the cleaners suffered a head wound, while the other was wounded in the hand. Both were women.

Source: SPA