At 8:30 p.m. Monday, with an electrical fire engulfing a North Bay Shore home, firefighters found siblings Luis Zayas and Angela Alvarez unconscious in a ground-floor bathroom. While Zayas, 17, died shortly thereafter, Alvarez, 16, remains in critical condition with smoke inhalation and thermal burns.

Although sensitive to the family’s grieving, authorities are concerned that “some alterations” to the single-family home may have contributed to the fire or impeded responders. “It’s obviously a multifamily dwelling,” said Islip Public Safety Commissioner Larry O’Leary, unsure of the number of residents.

While there was “no criminal culpability at the moment,” O’Leary said illegal conversions are a frequent concern: “It’s unfortunately become more common.”