MISSOULA (AP) — There isn’t enough evidence to prosecute anyone for anything in the February 2002 arson fire that destroyed the house of a Montana lesbian couple and their toddler son, the chief prosecutor said.

The investigation has hit a dead end, said Missoula County Attorney Fred Van Valkenburg.

“I’m basically making the determination that the arson investigation should be closed because we don’t have sufficient evidence to prosecute anyone,” he said.

FBI tests on two hoax anthrax letters sent to Carla Grayson and Adrienne Neff came back negative, he said.

The letters arrived two days before the early morning fire that destroyed their house and two days after they and another couple filed suit against the Montana University system for failing to provide equal benefits to same-sex and straight couples.

The FBI laboratory found no fingerprints and no DNA “of any kind whatsoever” on the letters, Van Valkenburg said. Any positive results could have led to federal charges for mailing the hoax letters and might have given local investigators a hint as to who torched the house.

The letter from the FBI said “it has been determined by both the FBI and the United States Attorney’s office that these cases should be closed,” Van Valkenburg said.

Carla Grayson said that she and Neff are “disappointed but not surprised.” They have since settled in at Ann Arbor, Michigan, and have no plans to return to Missoula.

“We’re still hoping that some day the arsonist will say the wrong thing to the wrong person and be turned in,” she said.

In the weeks and months after the fire — initially categorized as an attempted triple homicide — much of the attention given to the investigation turned to the women themselves. But they were never officially named as suspects.

Grayson said she and Neff believe the investigation into the arson fire was inefficient and insufficient, and that whoever destroyed their home is still out there.

“Whoever could be so coldly calculating and dismissive of life, particularly the life of a young child?” she asked.

“That person continues to be a danger to the greater Missoula community.”