Three days after launching it, the Maryland state prosecutor on Friday closed a criminal investigation into whether Montgomery County improperly used county resources during two ongoing referendum campaigns.

The ballot measures involve a local police labor law and a county hiring authority for people with severe disabilities. The county has created Web sites for the two initiatives. It also has put ads on its Ride On buses and distributed fliers about the police referendum.

The prosecutor, Emmet C. Davitt, closed the investigation because he found that the county acted in good faith because it received “not unreasonable” advice from its top attorney, Marc Hansen.

But in a letter to Attorney General Douglas Gansler, Davitt said he did “not entirely” agree with Hansen’s advice and sought an opinion from Gansler on how the government can use public resources during referendum campaigns, if it can at all.

Marc Zifcak, a former president for the police union that is fighting the police labor law, said in response to the letter that the union is disappointed that the office did not continue with the investigation.

“The county did what the county did, irrespective of intent,” Zifcak said. “The damage is done.”

County spokesman Patrick Lacefield provided reporters with a copy of Davitt’s letter to Gansler. Lacefield did not respond to a request for comment Friday.

The county police labor law, approved by the county council last year, would remove a method of bargaining that the police union has had for three decades. The union successfully put the law to a referendum in August.

The other referendum, spearheaded by council member Phil Andrews (D-Gaithersburg-Rockville), would create a county hiring authority that would promote and hire people with severe disabilities in county jobs.