A local prosecutor and his wife have been found dead in their home in the US state of Texas, two months after one of his assistant district attorneys was also shot to death in a parking lot one block from his office.

National and local law enforcement agencies were investigating the deaths of Mike McLelland and his wife, police spokesman Justin Lewis said late on Saturday.

Lewis said he could not discuss the investigation in further detail, including how the couple died and whether authorities believe their deaths are linked to the January 31 fatal shooting of another prosecutor, Mark Hasse.

The Dallas Morning News reported that Police Chief Chris Aulbaugh said the McLellands had been shot in their home and that although investigators did not know if their deaths and Hasse's were related, they could not discount it.

"It is a shock," Aulbaugh said, according to the paper. "It was a shock with Mark Hasse, and now you can just imagine the double shock and until we know what happened, I really cannot confirm that it's related but you always have to assume until it's proven otherwise."

A neighbour of the slain couple told the Associated Press that police squad cars were parked in the district attorney's driveway for about a month after Hasse was killed.

High-profile cases

Aulbaugh said recently that the FBI was checking to see if Hasse's killing could also be related to the March 19 killing of Tom Clements, corrections department head in the US state of Colorado, who was gunned down after answering the doorbell at his home. 

Evan Spencer Ebel, a former Colorado inmate and white supremacist who authorities believe killed Clements and a pizza deliveryman two days earlier, was killed in a March 21 shootout with Texas deputies about 160km from the most recent killings.

Hasse was chief of the organised crime unit when he was an assistant prosecutor in Dallas County in the 1980s, and he handled similar cases in Kaufman County, 53km southeast of Dallas.

McLelland had said Hasse was one of 12 attorneys on his staff, all of whom handle hundreds of cases at a time.

In recent years, Hasse played major roles in Kaufman County's most high-profile cases, including a conviction of a man who killed his former girlfriend and her 10-year-old daughter.

Source: Agencies