(Adds competition regulator's comments)
MEXICO CITY, April 19 (Reuters) - Mexico is investigating possible antitrust violations by intermediaries in auctions of the country's public debt market, the Federal Economic Competition Commission (Cofece) said on Wednesday, without naming any institutions in the probe.
The government sells hundreds of billions of pesos of securities every year and daily trades total nearly 100 billion pesos ($5.3 billion). Commercial banks and brokerage houses are the main participants in auctions of treasury bills, or Cetes, and other debt instruments.
Cofece said it initiated the ongoing probe nearly six months after finding signs that competitors might have agreed on or manipulated prices, restricted or limited supply or demand, or divided markets to gain an unfair advantage.
"This commission had knowledge of situations that constitute signs of possible antitrust practices," Cofece said in a statement.
"If there are agreements that affect the auction of government securities, the damage to the public treasury and to investors would be serious," said Cofece head Carlos Mena.
Financial institutions found guilty of antitrust practices could face fines of up to 10 percent of their income, and any individuals who assisted could face up to 10 years in prison, Cofece said.
Mexico's banking sector is led by BBVA Bancomer, Citigroup Inc's Citibanamex, Grupo Financiero Banorte and Santander Mexico. (Reporting by Anthony Esposito and Roberto Aguilar; Editing by Mitra Taj and Richard Chang)