Portland police say the city is enduring an unusual spike in violent crime that may trace its roots to drug use.

Police have reported seven incidents in which the perpetrators displayed a gun or a knife to commit a robbery, acting Chief Vern Malloch said at a news conference Tuesday.

Police have increased patrols in the West End, where most of the crimes have occurred, and are asking members of the public to provide any information they can. Meanwhile, detectives continue to investigate the crimes in an effort to identify those responsible. Asked whether there have been comparable spikes in the past, Malloch said he was not aware of any.

“We firmly believe – based on interviews we have done (of convicted robbers) in the vast majority, over 90 percent, of the time – they’re feeding a drug habit,” Malloch said.

Malloch’s comments came four days after a man tried to rob a woman at knifepoint in the parking lot of Shalom House on Gilman Street. The man demanded money, then pulled a knife when the woman said she didn’t have any. He continued to demand money, threatening her with the knife, until she said she might have some in the car, Malloch said.

The woman reached into her car and grabbed a handgun and scared off the robber, he said. The woman has a concealed weapons permit, Malloch said.

Less than a block away, the TruChoice Federal Credit Union was robbed on May 26 by an armed man wearing a disguise. The credit union has offered a $5,000 reward for information leading to the arrest and conviction of the robber.

“They really want to do everything they can to make sure the community and their community within the credit union is a safe place to be,” Malloch said.

Data provided by the Portland Police Department show that there were 62 robberies in the city in 2014, down 23 percent from the 81 that were reported in 2013. From Jan. 1 through May 28 of this year, there were 36 robberies. Those don’t include the Gilman Street attempt and a recent assault and robbery at Clark and Pine streets.

Malloch said it doesn’t appear most of the recent violent crimes are connected. Witnesses have given different descriptions of the attackers in most of the incidents.

“We’re concerned about it but we also don’t see any one perpetrator as responsible,” Malloch said. “The best method of solving crimes is when the public comes forward and offers us information.” He added that there’s very little chance a cruiser will be driving by when one of these crimes is occurring.

Police continue to investigate a homicide that occurred May 25 at 26 Market St. in the Old Port. Malloch said police have no new information to share on that case.

Police also are investigating a spate of car burglaries that happened Monday night and Tuesday morning in West Bayside and Parkside. A Portland Press Herald analysis of crime numbers last year found that the West End saw a higher percentage of the 714 car burglaries in the 12 months ending in February 2014 than other neighborhoods. The Parkside and West Bayside neighborhoods had comparatively few, though those neighborhoods had the highest rate of assaults during that period.

Malloch said residents should be aware of their surroundings and prepared to call 911 on a cellphone if they feel threatened. They also should be prepared to surrender their property if threatened with harm.

“The best advice we can give is comply with demands if you are a victim of robbery. The value of whatever money or cellphones or electronics or whatever you might have is not worth your life or potential injury to yourself,” Malloch said.

In the recent spate of robberies and attempted robberies, the only injuries occurred in the May 31 assault, attempted sexual assault and robbery of a 23-year-old woman on Clark Street near Pine Street.

Police ask anyone with information about the crimes to call 874-8533. Mobile phone users can text the keyword “GOTCHA” plus their message to 274637 (CRIMES) to leave an anonymous tip or go to the department website: www.portland-police.com and click “Submit an Anonymous Crime Tip.”

David Hench can be contacted at 791-6327 or at:

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