More than a dozen firefighting crews helped douse a second-alarm blaze on Linda Isle in Newport Beach on Saturday morning.

About 8 a.m., the first engine on the scene found flames showing through the second-story windows of a large house in the 100 block of Linda Isle Drive, the island's single street, Battalion Chief Todd Knipp said.

Most of the second floor was engulfed by flames, Knipp said, but no civilians or firefighters were hurt in the blaze.

The house was under construction, so nobody was home at the time of the fire.

The blaze did not prompt any evacuations, but the small island with limited access did present a logistical problem for the 13 engines and trucks that responded.

"Access was an issue for us just because we can't put all those units on," Knipp said.

Just six fire vehicles at a time were able to get onto the horseshoe-shaped island, but crews nevertheless put out the flames in about 20 minutes, Knipp said.

The blaze caused significant structural damage to the home, according to the fire department.

Investigators are looking into what caused the fire and so far have found nothing suspicious, Knipp said.

— Jeremiah Dobruck

Twitter: @jeremiahdobruck