The State Bureau of Investigation has opened an inquiry into how the son of former House Speaker Jim Black received contracts to provide pest control at three state prisons.

The inquiry comes after The News & Observer reported last month that Black Pest Control, a Charlotte company, had won the work despite charging roughly three times more for the work than the low bidder.

George Zaborowski, a former project manager for a subcontractor at two of the prisons, said that he was ordered to hire Black Pest Control at its price to satisfy a state lawmaker whose vote was critical for the prisons' construction.

Zaborowski said the order came from two officials with Centex Construction, which oversaw the prison projects for the state.

Wake County District Attorney Colon Willoughby initially saw no reason to look into the contracts. But Thursday, he confirmed that he wanted the SBI to conduct a "preliminary inquiry."

"Some of the matters that were publicly reported were things that called into question the bidding process," Willoughby said. "I felt like I needed a better understanding of what had gone on in order to make an informed decision about the necessity of a criminal investigation."

An attorney for Jon Black, the owner of Black Pest Control, said his client did not exert any undue influence to win the prison work. Black Pest Control was paid $124,000 to ward off termites at prisons under construction in Bertie and Greene counties. The company bowed out of a $73,600 contract to do similar work at a prison at Columbus County.

Centex has since been bought by Balfour Beatty Construction of London. Balfour officials do not dispute that Centex preferred giving the work to Black Pest Control, but only because it had done good work on two small bank branches Centex built in the Charlotte area.

It was not illegal to hire Black Pest Control despite its not being the low bidder.

The state legislation that authorized the three prisons' construction exempted Centex from having to follow public bid laws.

It is unclear how that language was added to the legislation shortly before it came up for a full vote in the House and Senate.

Jim Black, a Mecklenburg Democrat, is serving a five-year prison sentence and has been ordered to pay a $1 million fine after pleading guilty to state and federal public corruption charges. The crimes are not related to the prison construction.