Firefighter Matt Cottini has served for 12 years. Engineer Justin Lopez has served for 12.5 years. Firefighter Jake Ciulla has served for three years. Capt. Hunter Clare has served for 15 years. (Photos courtesy Peoria Fire-Medical)

More than three months after an explosion at an Arizona Public Service (APS) substation in Surprise injured four Peoria firefighters, the source of the incident remains to be determined.

An incident report, recently released by the Surprise Fire-Medical Department and obtained by Peoria Times, further detailed the response procedures to the April 19 incident at the McMicken Energy Storage facility near Deer Valley Road and Grand Avenue.

But few new details surfaced. The investigation is still in progress.

And the four injured Peoria firefighters — Capt. Hunter Clare, Engineer Justin Lopez and firefighters Matt Cottini and Jake Ciulla — are still


“All four of our firefighters are home and undergoing physical therapy,” Peoria Deputy Fire Chief Brewster said. “They still have a long road to recovery; however, they are improving daily.”

Brewster declined further interviews.

Peoria Fire-Medical spokesman Michael Selmer said at an April 22 press conference that Lopez sustained nose, skull, rib, right-leg tibia and fibula fractures as well as a collapsed lung. Clare suffered bilateral ankle and thoracic fractures, a possible wrist fracture, multiple burns and lacerations, and a scapula injury.

Cottini suffered head and jaw lacerations and burns as well as a knee injury. He was released from the hospital the day after the incident but readmitted with severe headaches the following morning. Ciulla received minor burns and lacerations, and was also released and readmitted that weekend with “full body aches and pains,” Selmer said.

Four Surprise firefighters were also injured during the incident, though they were at the time only held for observation, according to Surprise Fire Marshal Keith Tanner.

According to the new document, the incident began with reports of smoke. Fire crews including HazMat responded.

First responders witnessed “a steady stream of smoke” coming from a building south of the substation before the eventual explosion, which injured the eight firefighters.

They were transported to local hospitals.

In the report it was noted that fire personnel from Glendale, El Mirage, Phoenix, Sun City and Goodyear as well as the Arizona Fire & Medical Authority assisted during the response.

No APS employees were injured in the incident, APS spokeswoman Jill Hanks previously told Peoria Times.

But the lithium-ion battery facility will not return to operation, she added on August 7.

However, the monetary value of APS’ losses have not been confirmed publicly. According to Hanks, APS does not publicly disclose asset values of this time.

Though the damage is too severe, customers have not been impacted.

According to an August 8 press release, the most recent issued by APS, the investigation remains a partnership between APS, first responders, the system integrator, manufactures and third-party engineering and safety experts to investigate.

The cause of the “catastrophic (system) failure” is unknown.

However, the first phase of the investigation is reportedly complete, with all major equipment including 378 battery modules removed from the building.

During the current second phase of the investigation, APS will conduct a “comprehensive forensic analysis of key components from the storage system.”

Officials will also recreate the event timeline to determine what contributed to the system failure.

Some components — from a rack believed to be the source of the failure — have been removed and sent to a Scottsdale lab for examination.

They will then be sent to a forensic lab in Michigan. Results are expected next month.

The energy provider issued the following statement:

“We greatly appreciate the hard work and bravery of the first responders who were involved.

“While the recovery of the first responders injured on scene during the incident remains top of mind for all involved with the investigation, their progress and status will not be included in these updates.”

To follow APS’ investigation, visit