ADANA, TURKEY — A large number of Turkish troops and civilians on Sunday sealed off Incirlik Air Base, a military base used by the U.S. and functions as a NATO storage site. The lock down came a day before a key U.S. official’s scheduled visit.

Incirlik Air Base is located in the city of Adana in southern Turkey. The air base is mainly operated by U.S. and Turkish militaries. It is also one of the six NATO storage sites, and can store up to 90 warheads.

Local media reported that air base was sealed off by heavy vehicles such as trucks, and both civilians and police were involved. The action also alledgely fueled rumours of a second coup attempt, News.com.au reported.

Bloomberg reported that Turkish authorities restored access to the air base before U.S. Joint Chiefs of Staff Chairman Gen. Joseph Dunford arrived on Monday. The lockdown reportedly lasted for 4 hours.

Gen. Joseph Dunford is expected to hold talks with Turkish military officials in Ankara.