SECRET chambers dedicated to a mysterious “underworld” have been uncovered in an ancient pyramid.

Researchers have revealed they discovered a new tunnel and a cavity hidden below an archaeological site near Mexico City.

Details of the stunning discoveries were given in a statement from the investigators of the National Institute of Anthropology and History.

Veronica Ortega, the director of the Project of Integral Conservation of Plaza de la Luna, which is the central square in the complex, said the investigation is focused on a ritual space linked to the "underworld".

Mrs Ortega said the investigation into the cavity, which is believed to have been used as a chamber, will allow them to determine the connections that this old metropolis had with other regions of Mesoameric.

The discovery of the chamber and tunnel is a result of a initial study using electrical resistivity carried out around the Pyramid of the Moon in June 2017.

Electric resistivity methods are a form of geophysical surveying which help create an image of the subsurface.

These methods utilise differences in electric potential to identify subsurface material.

The cavity, which experts believe could have been dedicated to rituals, is 26 feet below the pyramid and is 49 feet in diameter.

The tunnel is located towards the south of the Plaza de la Luna and experts believe there could be another entry to the east.

The Pyramid of the Moon is the second largest pyramid in Mexico after the Pyramid of the Sun.

Its structure existed prior to 200 AD.

Studies from 2017 gave an indication of the possible existence of a chamber and the archaeologists have now confirmed the existence of the chamber.

The city of Teotihuacan is believed to have been established around 100 BCE.

It is believed to have been built by the Toltec before the Aztecs arrived.

In research carried out in the late 1980s at the site archaeologists Ruben Cabrera and Saburo Sugiyama discovered skeletons with cranial deformations along with objects from green stone.