MEXICO CITY (Reuters) -A Mexican regulator on Tuesday slapped three financial institutions with administrative fines but the government reiterated that despite U.S. sanctions on them for alleged money laundering, there was no conclusive evidence of wrongdoing.

Last month, the U.S. prohibited certain transactions with Mexico's CIBanco, Intercam Banco and Vector Casa de Bolsa as part of its fentanyl sanctions.

"If we have conclusive information that proves illicit activities of these three financial institutions, we will act with the full force of the law," the finance ministry said in a statement. "However, to date we have no such information."

The three have denied the U.S. allegations and Mexico's government has said that the U.S. Treasury had not provided proof to back up its claims.

In late June, the banking regulator stepped in to manage the three firms.

The combined 185 million pesos ($9.8 million) in fines imposed by the country's banking watchdog were due to "non-compliance in administrative processes," the ministry said.

Many of the fines on Intercam and CIBanco were related to money-laundering prevention, while Vector mostly faced fines for failing to comply with obligations in publishing information.

Intercam was fined 92.15 million pesos, while CIBanco was fined 66.61 million pesos and Vector will need to pay 26.46 million pesos.

($1 = 18.8499 Mexican pesos)