Armed police officials swooped into the Sabiha Gökçen airport in Istanbul, Turkey after an explosion Wednesday killed one person and injured another, local reports said. The cause of the blast was not clear but the country’s officials are investigating if it was a terrorist activity.

The two victims were the cleaning staff for Pegasus Airlines, and were working on a plane when the explosion happened. No passengers were present at the location when the blast occurred at 2:05 a.m. (7:05 p.m. EST, Tuesday) and operations continued normally after the blast, Reuters reported. Police officials, armed with rifles and protective vests, maintained strict security near the entrance gates following the blast.

"Of the airport cleaning staff, Canan Celik Burgucu, 33, suffered an injury to her hand and Zehra Yamac, 30, to her head," Pegasus said, in a statement, cited by the state-run Anadolu Agency. The killed woman was identified as Zehra Yamaç.

After the blast, the women were taken to the Pendik Research and Training Hospital while the governor of Istanbul Vasip Sahin said that an investigation was ongoing into the cause of the accident. The airport also said, according to Reuters, that there were no problems in the take-offs and landings.