Mexican fixed-line giant Telefonos de Mexico has filed a complaint against Spain's Obrascon Huarte Lain, accusing the construction company of damaging its fiber-optic network and interrupting phone service for thousands of customers of its sister mobile operator, Telcel.

OHL's local unit cut fiber-optic lines in the western part of Mexico City, where it is building an elevated highway, knocking out service for customers of Telcel and other companies, Telmex said in a statement Thursday.

Telcel, Mexico's largest wireless operator, and dominant fixed-line company Telmex are both subsidiaries of America Movil, which is controlled by Mexican multi-billionaire Carlos Slim.

Telmex filed the complaint Thursday against OHL Mexico and its subcontractor, Constructora GAM, accusing them of "attacks on the general communication channels" and damage to another's company's property.

Telmex also said OHL did not report Wednesday's damage and instead covered it up with steel sheets, "which made it difficult to locate the cut in the fiber optic line and repair it immediately."

The company said its technicians worked for hours to repair the fiber-optic line and re-establish phone service to customers.

In July, OHL was forced to pay a 10-million-peso ($860,000) fine for a work-site accident in which three large beams fell to the ground and caused injuries to three workers and a massive traffic jam.

The Spanish company paid the fine to the Mexico City government to avoid cancellation of its contract for the 10-kilometer (6-mile) stretch of highway popularly known as the "second floor" of the capital's Periferico freeway.