Federal investigators on Thursday tried to establish what exactly caused the collapse of the Minneapolis bridge last year. The main problem – “critical factor” - that caused the deadly collapse was related to serious design errors.

The steel plates connecting the bridge’s beams were wrongly designed in the Minneapolis bridge and led to the tragic incident which occurred in 2007. National Transportation Safety Board investigators concluded that the tragedy was unavoidable because the way the U-10 steel gusset plates were designed.

The federal investigators are expected to give a ruling near the end of a two-day hearing during which they will discuss what they found out about the deadly collapse and what must be done. The political factor is not missing of course; the Democrats in Minnesota have been harshly criticizing the state's Republican governor, Tim Pawlenty. However, board members said they would keep politics out of it.

"We are here, not to protect other agencies or other organization, we are not here to point fingers or to lay blame, or find fault ... We are not here to push personal agendas. We're here to seek the truth," said board member Robert Sumwalt.

A previous interim report carried out in January 2008, pointed out the exact same cause for the collapse: flawed design. 16 gusset plates, which connect steel beams, broke because they had 50% of the required thickness.

The collapse of the I-35W bridge into the Mississippi River on Aug. 1, 2007 during evening rush hour caused the deaths of 13 people and the injuring 145.

When the bridge collapsed, the state had a $1 million-per-incident liability cap in effect. After the incident, Sen. Ron Latz proposed an amendment to enable the victims to sue the state or enter into settlement talks for up to $300,000 each. The amendment had no success because it would have put the victims through a long legal process and left those suffering from serious wounds with uncovered costs.