The estate of Oklahoma City energy industry magnate Aubrey McClendon is rejecting a Tulsa man's $500,000 claim as a forgery.

Retired Tulsa businessman Thomas Quinn says he loaned McClendon the money in 1991 and filed a promissory note saying full payment was due Dec. 1, 2015. Quinn says in a January 2016 letter to McClendon that he had no objection to extending the deadline by a year.

Quinn sued after estate attorneys rejected the claim. A response to the lawsuit filed earlier this month says the contract is a forgery.

Quinn denied the allegation and told The Journal Record (http://bit.ly/2g5oKHL ) the promissory note is also signed by a witness.

McClendon died March 2 when his SUV crashed into a bridge in Oklahoma City a day after he was indicted for alleged bid rigging.