Federal investigators have joined the probe into the Broadview Heights house fire that killed North Royalton firefighter Ryan Milligan on Nov. 2.

The Ohio State Fire Marshal's Fire and Explosion Investigations Bureau is leading the investigation in partnership with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), Cleveland 19 reported, citing the State Fire Marshal's office. A spokesperson for the State Fire Marshal said the fire's cause remains undetermined, according to Fox 8.

The State Fire Marshal's news release did not explain why the ATF was brought in. Fox 8 reported it had reached out to ATF officials for comment.

PREVIOUS COVERAGE | North Royalton firefighter dies battling Broadview Heights blaze

The Cuyahoga County Medical Examiner's Office said an autopsy was conducted on Milligan but no cause of death has been released. "No further information is available at this time. Still pending," a spokesperson for the office said, according to Fox 8.

Milligan, 36, of Seven Hills, died the evening of Nov. 2 while battling the blaze in the 2100 block of West Royalton Road. Multiple first responders were called to the scene before 9 p.m. A second North Royalton firefighter, Andrew Protsman, 38, of Parma, suffered serious injuries in the same fire and remained hospitalized as of Nov. 5, Cleveland 19 reported. Earlier reports said Protsman was in stable condition and expected to recover.

Five Broadview Heights police officers were also treated for smoke inhalation and later released from the hospital, Broadview Heights Police Chief Don Polick told Fox 8 in a media release. Two people were inside the home at the time of the fire but escaped.

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Firefighters from North Royalton, Broadview Heights, Seven Hills and Brecksville all responded to the scene, according to Cleveland 19.

State Fire Marshal Kevin Reardon said the firefighters "answered the call to serve others without hesitation, placing themselves in harm's way to protect their community."

Milligan joined the North Royalton Fire Department in August 2016 and had recently signed up for a future fire lieutenant promotional exam, according to North Royalton Mayor Paul Marnecheck. A 2009 graduate of Normandy High School, Milligan also served with the Seven Hills Fire Department. He is survived by his wife, Laura, and two young children.

In coverage published Nov. 5, Spectrum News 1 reported Marnecheck said, "Not only did North Royalton lose them, but a family lost a brother, son, and father. We are going to work with the family."

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Gov. Mike DeWine ordered flags at all public buildings in North Royalton and at several state buildings to fly at half-staff until sunset on the day of Milligan's funeral.

Visitation is scheduled for Sunday, Nov. 8 from 4 p.m. to 8 p.m. at Grace Church on Pearl Road in Middleburg Heights. The funeral service is set for Monday, Nov. 9 at 11 a.m. at the same location, according to Milligan's obituary. In lieu of flowers, the family has asked for memorial contributions to Blue Coats, which supports families of fallen safety force members.