Drug users who overdose and those who call 911 for help would be immune from prosecution under a bill that breezed through the Minnesota Senate on Tuesday by unanimous vote.

But the measure, crafted as a response to the surge of heroin overdoses in the state, is triggering alarm among prosecutors and law enforcement officials, who say the immunity provision could protect drug dealers and other criminals.

The bill, which passed in minutes with little debate, would allow first responders, law enforcement and some nonmedical professionals to administer Narcan, a drug that can counteract the effects of a heroin overdose within minutes.

Hennepin County Sheriff Rich Stanek, who was among those supporting the Narcan provision, said that offering immunity goes "too far to the other side." As a result, he may not have his deputies carry the lifesaving drug.

"We got into this for the right reason, which was to save lives," he said of his initial support for the bill. "We did not get into this to save lives and get immunity for everyone."

The number of heroin deaths in the Twin Cities has tripled since 2011, to 63 last year, with most of them taking place in Hennepin County. Hospital emergency rooms recorded nearly 3,500 visits from heroin users in 2011.

The bill is nicknamed "Steve's Law," after Steve Rummler, who died of a heroin overdose in 2011 following an addiction to prescription painkillers.

The Minnesota County Attorneys Association says it will attempt to intervene before the bill goes to the House and then Gov. Mark Dayton's desk. Prosecutors say they would consider granting immunity in lower-level drug cases, but not across the board.

The bill's sponsor, Sen. Chris Eaton, DFL-Brooklyn Center, said both measures are necessary. Eaton's daughter, Ariel Eaton-Willson, died in 2007 of a heroin overdose in a Burger King parking lot at age 23.

Eaton-Willson's friend, instead of immediately calling for help, cleared out the car they were in, throwing away needles that could have been used as evidence.

Eaton, a registered nurse, told the Senate said that if medical professionals armed with Narcan had been called right away, her daughter's life might have been saved.

Eaton said law enforcement's concerns that the immunity provision could jeopardize drug investigations may be overblown.

She said supporters called four sheriff's offices and found that none had made arrests as a direct result of 911 calls from an overdose scene.

"If nobody calls [911], the police will never get there and there's nobody arrested," Eaton said. "Most of the companions of the people using these drugs leave and let the person die alone," she said. "This law will not result in fewer arrests — they aren't happening anyway."

The bill closely mirrors one signed into law last year that protects underage drinkers who call 911 to report a medical emergency, as long as they're the first person to make a report, provide contact information, and remain at the scene to cooperate with authorities.

'This is not easy stuff'

John Kingrey, executive director of the Minnesota County Attorneys Association, called Steve's Law "the most challenging bill I've had to testify against in my 14 years here. You're expressing concern on behalf of law enforcement and prosecutors after these family members have lost loved ones to drug overdoses. This is not easy stuff to testify to."

Kingrey said immunity makes sense for lower-level drug offenses. But, he added, "when law enforcement happens upon a very chaotic scene, to not allow law enforcement to place people under arrest until they can sort through the facts is very troubling to us."

The House version of Steve's Law at one point didn't contain the immunity language, but is now similar to the Senate bill. Lexi Reed-Holtum, Rummler's fiancé and vice president of the Steve Rummler Hope Foundation, said that foundation's research has shown that immunity has often led law enforcement to the source of the drug problem, rather than exacerbating it.

"We have vetted this issue with 14 other states that have a good Samaritan law, asking them, 'What kind of unintended consequences are you having?' " Reed-Holtum said. "The response we have gotten back overwhelmingly is not only this not doing harm, it is actually building a bridge that did not exist before."

Sen. Bill Ingebrigtsen, R-Alexandria, was initially the lone "no" vote on the Senate bill Tuesday before changing his mind.

"I've always had a little problem with the immunity part of it, however, quite frankly, some of these calls would not happen unless we pass a law like this," he said afterward.

Ingebrigtsen added, "the bottom line is, if nobody's gonna call, somebody's gonna die."