Turkish prosecutors have denied a media report that they have concluded an attack on Istanbul's second airport last month that killed an aircraft cleaner was caused by mortar fire.
The state-run Anadolu Agency reported earlier on Thursday (local time) that four mortar rounds were fired from around two kilometres away from Sabiha Gokcen airport in the December 23 attack, citing prosecutors in Istanbul.
However, the Istanbul Anadolu prosecutors office, which covers the Asian side of the city where the airport is located, said in a statement later the investigation had not yet been concluded.
"Our file does not include information that the attack was carried out by mortar fire, and no statement has been made by our office to any media," the prosecutors' office said.
The attack at Sabiha Gokcen, which handles both domestic and international flights and is owned by Malaysia Airports, fatally wounded a cleaner on a plane belonging to budget carrier Pegasus.
Turkey has stepped up security at its international airports as it has tried to prevent foreign fighters, hidden among the millions of tourists who visit each year, seeking to cross its territory and join the ranks of Islamic State in Syria.
There has been no suggestion, however, that Islamist militants were behind the attack.
A Kurdish militant group once linked to the outlawed Kurdistan Workers Party (PKK), which has fought a three-decade insurgency for greater autonomy in Turkey's southeast, claimed responsibility several days later.
The Kurdistan Freedom Hawks (TAK) has in the past claimed some attacks outside the PKK's regular area of operation in the mainly Kurdish southeast, such as a 2012 assault on a military bus that killed two soldiers in a coastal resort town.
The Anadolu Agency cited prosecutors saying they had not yet concluded who was responsible for the attack.