It's a case that won't - and some say shouldn't - go away.

Five and a half years after some $80,000 worth of marijuana mysteriously disappeared from the Dracut police station, officials are still trying to determine who took it. Recently, several officers were ordered to take lie detector tests to help determine whether any of them could be linked to the missing drugs.

Local officials say the case has caused the town embarrassment, giving the impression that police have been unable or unwilling to solve the crime and that they might even have been involved in it.

"It gives the town a black eye," said Robert Cox, chairman of the Dracut Board of Selectmen.

At the same time, some say it's important to get at the truth.

"We need to come to some understanding of the truth, whether the police were involved or not - hopefully not," said Dracut Selectman George Malliaros, who first called for the lie-detector tests to be administered.

The probe is infuriating police union officials, who say it's time for it to end so officers can return to focusing on their work.

"I think everybody's had about enough of this investigation," said Anthony L. Archinski, regional vice president of New England Police Benevolent Association, the local police union's parent organization. "I think productivity has come to a screeching halt."

Instead of the probe to identify culprits, Archinski said, the town should call in an independent fact-finder to determine whether the theft could have been prevented and whether any police policies or procedures were violated.

Archinski, who retired as a lieutenant from the Dracut Police Department at the end of last year, having also served as local police union head, said the department's leaders are trying to swing the spotlight from what he deems their failure to properly secure the stash.

He said the marijuana, confiscated from suspects in a drug case, was being kept in a padlocked outdoor storage container in the back of the old police station on Lakeview Avenue. The new police station has adequate secure storage for confiscated evidence.

"The administration needs to stand up and take responsibility for it," Archinski said.

Dracut Police Chief Kevin M. Richardson and Deputy Chief David Chartrand did not return phone calls seeking comment about the missing marijuana and the investigation.

This is the third time officials have tried to determine what happened, having come up dry the previous two attempts. As the latest probe unfolds, townspeople are shaking their heads in wonder, says Cox.

"For the taxpayers, it's been a coffee table conversation no matter where you go," he said. "They're saying, 'What happened? How come nothing has transpired?"'

While Cox understands the union's viewpoint, he also says the situation has been difficult for Richardson, who was appointed chief in 2005, two years after the crime, but still feels obligated to pursue the investigation.