Municipal workers carrying out sewage work in Turkey's central Kayseri province have discovered a 20-meter-deep tunnel, which officials say could lead to an ancient underground city, reports said Monday.

The workers discovered the tunnel after digging in Tomarza district and stopped all sewage work afterward.

They immediately informed the police, who found out that the tunnel is one-meter-wide and 20-meters-deep with stair-like pits on the sides. The police then cordoned off the area as part of security precautions and informed the Kayseri Provincial Cultural and Tourism Directorate for further examinations.

Local headman Ahmet Doğan told reporters that experts noted the tunnel could lead to an ancient underground city.

"If there is indeed an underground city in our neighborhood then we will do whatever we can to make sure that it is unearthed and opened to tourism," Doğan said.

Another ancient underground city with 52 chambers was discovered in Kayseri in 2017. That underground city was unique as it was built in a horizontal manner contrary to other underground cities in nearby Cappadocia.

Underground cities were built by ancient peoples as a means to seek refuge from invasions. They offered living space, transportation, food storage, drainage and more.

Cappadocia in Turkey is particularly famous for the Kaymaklı and Derinkuyu underground cities, which were carved out of unique geological formations and have become popular touristic attractions.