LYNN – Police are investigating whether fentanyl, a chemical that enhances the potency of heroin, may be to blame for a string of six overdoses – three of them fatal – throughout the city within 48 hours this weekend.”We’re thinking fentanyl … it showed up in the city this fall,” Lynn Police Chief Kevin Coppinger said Sunday afternoon.He said the incidents do not appear to be related; but the chief could not recall the city experiencing so many fatal overdoses in such a short period of time.”The demographics are different and the deaths occurred in three totally different locations,” Coppinger added.Police reported to responding to an overdose at 11:14 p.m. Thursday on the 100 block of Newhall Street; at 12:01 a.m. Friday on Graybriar Lane; at 4:32 a.m. Friday on Lewis Street; at 4:47 a.m. Friday on North Federal Street; at 9:58 a.m. Friday on Broad Street; and at 7:40 a.m. Saturday on Beede Avenue.Police said the Graybriar Lane, North Federal Street and Lewis Street overdoses were fatal.Coppinger identified the deceased as a 28-year-old white male; a 44-year-old black male; and a 38-year-old white male. A 21-year-old Hispanic male and a 48-year-old white male survived the overdoses. The demographic information of the Beede Avenue victim was not available Sunday.Police have long warned about a heroin epidemic that has caused overdoses to reach new records each year since 2010 and that has particularly increased in the last three years.Police recorded 71 overdoses in 2010, the last year that the number of annual heroin overdoses decreased, according to department statistics. Since that time, Lynn Police recorded 89 overdoses in 2011; 118 overdoses in 2012; and 189 and 280 overdoses in 2013 and 2014, respectively. The number of fatal heroin overdoses has generally followed this trend – with the city recording 9, 24, 19, and 35 fatal overdoses, respectively, in 2011 to 2014.Law enforcement and public safety officials, public health workers and legislators are trying to address the epidemic through treatment, prevention and education, legislation and distributing nasal Narcan, a drug that can reverse an opioid overdose.But the epidemic continues to grow. Heroin remains readily available, as cheap as $5 a hit, and deadly, particularly for those who have not built – or who have lost – a tolerance for the drug.That makes the presence of fentanyl – a colorless, odorless, tasteless chemical that is added to heroin to increase its potency – particularly concerning to law enforcement.Police first confirmed fentanyl reached the city late last fall, when the drug was detected during an autopsy of an overdose victim. Police also seized pure fentanyl in a December raid, Coppinger said.Heroin is not just a problem in Lynn, however. Essex County recorded 66 fatal heroin overdoses in 2013, and 145 fatal suspected heroin overdoses in 2014, according to State Police. This year there have already been 30 suspected fatal heroin overdoses in Essex County between Jan. 1 and Feb. 28, Essex District Attorney Jonathan Blodgett’s Office said Sunday.