The IPC index hit a nadir of 43,616.50 points in early trading before rebounding somewhat to trade down 0.38 percent on the day. America Movil shares were off 2.1 percent at 13.66 pesos.

The company recently announced disappointing results, heaping pressure on the company owned by Mexican billionaire Carlos Slim and shining a light on some of its less profitable investments, such as its stake in Dutch telecom company KPN.

America Movil's shares have lost nearly 14 percent since it reported results on Feb. 12.

"America Movil, with the influence it has, is pulling the IPC down," said Gerardo Copca, head of analysis at MetAnalisis in Mexico City. "Nobody liked their report or their involvement with KPN. There is also a lot of doubt surrounding future regulation of Mexico's telecommunications sector."

Separately, Mexican homebuilders on Monday rebounded from the fallout of last week's downgrade warning by Fitch Ratings.

The ratings agency put Geo, Urbi and Homex on a negative ratings watch, citing cash flow problems, lack of government support for the sector and a decline in investor confidence.

Shares of Urbi were up nearly 8 percent, while Geo shares were up more than 5 percent. Homex shares were up over 10 percent.