Colombia's President Juan Manuel Santos was presented with an official questionnaire from the country's National Electoral Council.

It will serve as testimony as the council investigates Santos' alleged election campaign ties to a scandal-plagued Brazilian construction company.

The president agreed to voluntarily cooperate in the probe examining his campaigns in both 2010 and 2014. The investigation is looking into contributions allegedly received from Odebrecht – already marred in scandal.

Santos' former campaign manager, Roberto Prieto, has admitted he funneled illegal funds from Odebrecht into the 2010 campaign. Prieto has also acknowledged Odebrecht paid 400,000 US dollars to a vendor to print campaign posters in 2014.

In March, Santos publicly apologized for the 2010 use of illegal funds, though he denied knowing anything about the transactions at the time. What Santos knew and when he knew it are likely to be at the heart of the National Electoral Council's questionnaire delivered to Santos on Monday.

While Santos has not commented on his testimony, he did talk about the investigation in a radio interview on Monday morning insisting Odebrecht was not rewarded during his time in office.

"If you look at Odebrecht during my government, they never received preferential treatment. Because of 22 bids they only won one or two projects," Santos said.

According to a United States investigation, Odebercht doled out nearly 800 million US dollars in bribes across four continents. The Brazilian firm is involved in the largest global corruption scandal in modern history.

Whether or not the firm bribed Santos' campaign, fallout from the Odebrecht scandal is impacting the region.

According to American bond rating company Moody's, Odebrecht's actions have scared investors away from doing business in Latin America – significantly undermining infrastructure and energy projects.

"In the very short term it is possible that they are saying 'let's stop investments in 2017' because they are waiting to analyze the political risks. What is at play is that there is a lot of uncertainty regarding the elections in 2018. The political risk may weigh heavier than the simple issue of corruption," economist Jorge Gaitan Villegas said.

Based on the president's testimony and other information collected during a preliminary investigation, the National Electoral Council will decide whether or not to open a formal investigation into Santos' election campaigns.