Schock sold his home to an executive at Caterpillar Inc., in 2012 for more than three times its assessed value, the liberal website Blue Nation Review reported last week. Caterpillar is headquartered in Schock’s district and the executive, former vice president Ali Bahaj, had donated to Schock, the website said.

Citizens for Responsibility and Ethics in Washington said the Office of Congressional Ethics should investigate whether the sale violated federal law and House rules.

The congressman has said the price was in line with other nearby properties. Schock also told reporters during a stop in Peoria on Friday that his real estate agent handled the transaction and he never spoke to the buyer.

“There’s nothing there,” Schock said.

Schock bought the vacant property in Dunlap, on which the home was built for $128,250 in 2003, according to property records.

The 4,100-square-foot home – with four bedrooms and three fireplaces – was completed in 2007, records show. The following year Schock won his bid for the U.S. House of Representatives.

Schock said the home was listed for 4 years before it sold in 2012 for $925,000. He noted there were other homes in the area that sold for more, and that the price per square foot of comparable home sales “were right in line with what everything was selling for at that time.”

A review of property records by The Associated Press found between 2011 and 2013, homes of comparable size in the neighborhood consistently sold for three times their assessed value, or more. That includes one 5,400-square-foot home on more than half an acre – about double the size of Schock’s lot – that sold for $1.07 million.

But Schock’s home sold for about $225 per square foot – about $50 to $75 more per square foot than other homes in the same area that were listed at similar size and condition.

Bahaj and his wife donated a combined $4,600 to Schock’s campaign in 2008, the maximum allowable contribution, and Ali Bahaj gave $1,000 to the congressman’s joint fundraising committee last year, according to reports filed with the Federal Election Commission. Bahaj also has donated to Caterpillar’s political action committee, which has supported Schock.

Schock’s spokesman did not immediately respond Monday to a reporter’s request for comment about the complaint.

Schock has also faced questions over his lavish office decor, and an aide who posted racially charged comments online. The aide resigned.