According to the Mayan inscriptions, the Earth will be beset with untold disaster in 2012, on either the 21st or 23rd of December.
Until now, most experts had cited just one surviving reference to the date, but Mexico's National Institute of Anthropology and History says in a statement that there is in fact another apparent reference to the date at the nearby Comalcalco ruin.
The only known reference to the so-called Apocalypse until now has been a date inscribed in Mayan glyphs, a stone tablet from the Tortuguero site in the Gulf coast state of Tabasco.
The new reference is found on the carved or molded face of a brick. Comalcalco is unusual among Mayan temples in that it was constructed of bricks.
The second reference was actually discovered several years ago, but has been the subject of intense and discreet study until the announcement by the institute of its existence.
According to the "Comalcalco Brick," as the second fragment is known, the world will indeed be struck by a major catastrophe toward the end of December, but not all Mayan experts are convinced.
David Stuart, a specialist in Mayan epigraphy at the University of Texas at Austin, told the Associated Press the date inscribed on the brick "is a Calendar Round, a combination of a day and month position that will repeat every 52 years."
The brick date does coincide with the end of the 13th Baktun; Baktuns were roughly 394-year periods and 13 was a significant, sacred number for the Mayas. The Mayan Long Count calendar begins in 3114 B.C., and the 13th Baktun ends around Dec. 21, 2012.
Stuart added that the inscription could correspond to past events as well, not necessarily one in the future.
"There's no reason it couldn't be also a date in ancient times, describing some important historical event in the Classic period. In fact, the third glyph on the brick seems to read as the verb huli, 'he/she/it arrives'."
Unlike the inscription on the stone tablet from the Tortuguero site, the Comalcalco reference contains no future tense, which some experts say makes it more of a historical reference than prophetic one.
Both inscriptions were carved around 1,300 years ago, with the Tortuguero inscription describing something that is supposed to occur in 2012 involving Bolon Yokte, a mysterious Mayan god associated with both war and creation.
Some read the last eroded glyphs as perhaps saying, "He will descend from the sky."
The Comalcalco brick on the other hand, is odd because the molded or inscribed faces of the bricks appear to have been laid facing inward or covered with stucco, suggesting they were not meant to be seen.
The Institute of Anthropology and History, however, has long held that Apocalyptic rumours are a Westernised misinterpretation of Mayan calendars and that saw time as a series of cycles that began and ended with regularity, but with nothing apocalyptic at the end of a given cycle.
News of the discovery of a second reference, however, has lit up Internet forums across the world, with many speculating on the alleged impending disaster.
In an effort to address such rumours, the institute is organizing a special round table of 60 Mayan experts next week at the archaeological site of Palenque, in southern Mexico.
The round table discussion aims to "dispel some of the doubts about the end of one era and the beginning of another, in the Mayan Long Count calendar", according to a press release.