01/28/2013 02:29 pm ET

Carbon Monoxide Leak In Rogers Park Suspected In Deaths Of 2 Women From Same Building

A family in Rogers Park on Chicago's North Side is coping with the loss of two members after a woman and her 18-year-old granddaughter died from what is believed to be a carbon monoxide leak.

Fire crews responded to the four-unit apartment building in the 2500 block of West North Shore Avenue around 10:30 a.m. Sunday, according to NBC Chicago. At the scene, 77-year-old Rasheeda Akhter was in cardiac arrest and died less than an hour later at an area hospital.

An ambulance was also called for Akhter's granddaughter, Zanib Ahmed, reports the Tribune. Just hours after losing Akhter, the family also lost Ahmed, who died at Swedish Covenant Hospital around 9 p.m.

Chicago Fire Department spokeswoman Meg Ahlheim said crews checked carbon monoxide levels in the building but didn't find evidence of a leak. The Tribune reports fire crews returned once again after a 74-year-old in the building was found unresponsive around 3:45 p.m. The second pass-through found a positive reading for "a low level of carbon monoxide" near a boiler in the basemen t— though there were still no indications of a leak in the residential units.

NBC said five other children were taken to the hospital for observation.

Peoples Gas was called to fix the boiler, and a spokeswoman told the Sun-Times the company was "supporting" fire officials in the investigation.

An official cause of death won't be determined until the Cook County Medical Examiner's office completes autopsies on Monday.