Investigators in the federal-parish corruption investigation of the Bossier Parish school system's maintenance department have been questioning residents in Plain Dealing -- following a trail of air conditioners from a Bossier City business that is at the heart of the probe of why the school system let millions of dollars in taxpayer money go to one business.

The FBI and Bossier sheriff's detectives want to know if the air conditioners -- which were installed in a dozen or more homes around the North Bossier Parish town -- were kickbacks to a school system employee who was being rewarded for funneling large amounts of work to one company, according to individuals questioned by investigators said. None of those who paid to have new air conditioners installed is suspected of any wrongdoing.

Also questioned was Bossier Parish Police Juror Winfred Johnston, whose son was a supervisor at the school system's maintenance office, and the son is a target of the investigation. Johnston, who installed some of the air conditioners, denied any wrongdoing.

The Justice Department is looking into whether some school maintenance employees took kickbacks in return for funneling work to Air Repair, a Bossier City company that got $6 million worth of air conditioning work from the school system in the past three years. They also are looking into whether inflated bills were submitted and whether the school system was billed for work that wasn't done. No charges have been filed.

In the Plain Dealing aspect of the investigation, authorities tracked one air conditioner to the home of former mayor David Smith.

Smith said Winfred Johnston, a longtime air conditioning man, replaced his unit after it was hit by lightning in March. Smith said he paid $3,000 for the job.

Johnston said his son, Randy, an air conditioning and heating supervisor for the school system, acted as a go-between and got the air conditioners from Air Repair.

"I give Randy the money," Johnston said of his son, who is among four school system employees who have been suspended amid the investigation. "He told me they had them on consignment at the warehouse down there, and the more they sold the cheaper they got them; and he'd sell them to me for cost plus 10 percent."

Authorities want to know if school system employees accepted free air conditioners in return for letting one company get so much of the work installing new air conditioning units in schools.

Winfred Johnston said he was not involved in any kind of kickback scheme. He was just installing air conditioners.

Randy Johnston's attorney, Peter Flowers of Shreveport, declined comment on the investigation of his client but said Winfred Johnston was never a part of what went on at the maintenance department.

In addition to Justice Department investigation, the state legislative auditor's office is reviewing accounting procedures at the Bossier school system's central office. They want to know about the oversight of so much money going to one company. One person briefed about the audit said there could be more than a quarter of a million dollars in overpayments.

The FBI is also investigating a mold remediation project at Haughton Middle School. Air Repair, which had the contract to do emergency work for Bossier schools, got the $1 million, no-bid job.

At the time it got the job, Air Repair did not have a mold-remediation license. It got the license the day the work started, the state board that licenses contractors said.

School Board records show Air Repair had already bought materials before it got the job, and the FBI and Bossier sheriff's investigators want to know if school system employees decided in advance who was going to get the job, said two people who have been questioned by investigators and spoke on the condition they not be identified.