WASHINGTON -- A reporting error in Sen. Amy Klobuchar's campaign contributions disclosures sparked a request from the Federal Elections Commision this week to clarify whether the Democratic senator was taking excessive contributions from the airlines industry.

In a letter to Klobuchar's campaign treasurer dated May 31, federal officials say that Klobuchar's filings show the senator taking excessive contributions from both a top airlines lobbyist and one of the industry's Political Action Committees called the Air Line Pilots Association.

Individuals or political committees may not make contributions to federal candidates in excess of $2,700 per election. Because that means a primary election and then a general election, individuals can give $5,400 total to a candidate. PACs can donate $5,000 per election or $10,000 total for a primary and a general election.

Klobuchar's next U.S. Senate election is in 2018.

Campaign staffers said it was a human error and a staffer did not mark "primary" or "general" in the paperwork correctly. They say they will fix it in the next filing due to federal officials July 15 for the second quarter.

The Air Line Pilots Association has maxed out in contributions to Klobuchar, records show.