The mysterious disappearance of Jeffrey and Jeanette Navin, the owners of Westport-based J&J Refuse who have not been seen since Aug. 4, had been a missing person case — until police found a bullet hole and blood in one of their vehicles, a law-enforcement source close to investigation said Monday.

At that point, on Aug. 10, police in the couple’s hometown of Easton requested that the State Police Western District Major Crime Squad take over the investigation.

Since that time State Police investigators have come to Superior Court seeking to have about a dozen search warrants signed, allowing them to search the Bridgeport home of the Navins’ son, Kyle, and landfills and farm fields.

Meanwhile, police found a white Mitsubishi work truck and a Mercedes E320 in the driveway of the Navins’ home.

The couple’s blue 2003 Dodge Ram pickup truck was discovered Aug. 9 parked in a commuter lot next to the Exit 42 off ramp to the Merritt Parkway in Westport. The passenger-side window was smashed and there were shards of glass on the ground, police said.

“Things really began to heat up once they found that bullet hole and blood,” the source said.

On Saturday, for instance, State Police said that a search by detectives of the Putnam ash residue landfill, operated by Wheelabrator Technologies, had “revealed no human remains at this point.” The landfill was searched in an effort to rule it out as a possible location of remains or other evidence in the case, according to the statement by State Trooper Kelly Grant.

Police sources also said the couple’s son, Kyle Navin, has been staying with friends in Westport and has refused to cooperate with Stae Police, other than an initial statement in which he denied knowing where his parents are.

Jeffrey Navin, 56, is the president of J&J Refuse. Jeanette Navin, 55, is a Weston Intermediate School library paraprofessional. Kyle Navin is operations manager of the refuse company.

On Aug. 7, Laura Thompson and Annie Navin, the wife of Jeffrey Navin’s brother William, a partner in trash business, reported the couple missing.

Jeffrey Navin had not told anyone that he and his wife were going away, according to Easton police.

Later that day police spoke to Kyle Navin.

“The last time he saw his parents was on Tuesday morning when they came to visit him,” Easton police stated in a search warrant affidavit. “Kyle stated that he has a broken back and is unable to work right now. His parents asked if he wanted to go out to dinner that night, but he told them his back was hurting and he didn’t want to go out.”

Police said Navin suggested the couple might have gone to New York for dinner.

“Kyle stated his father always takes small trips like that if they feel like it,” police stated in the search warrant affidavit.

Police sources confirm that Kyle Navin has a legitimate back injury and has a scheduled surgical procedure.