PORT ANGELES — A suspicious fire at Port Angeles High School’s automotive building early Tuesday morning that appeared to begin on the roof was extinguished before flames reached inside the structure, authorities said.

Damage to the building could exceed $75,000, school district spokeswoman Jennifer Sperline said.

Deputy Police Chief Jason Viada said Tuesday afternoon that the fire may have been caused by a mortar firework.

“That’s what it appears to be at this time, although we haven’t verified that 100 percent yet,” he said.

The blaze at the school’s 304 E. Park St. campus was of suspicious origin, city Assistant Fire Chief-Fire Marshal Mike Sanders said.

“There were no other sources of ignition in the area such as outlets and electrical boxes and things of that sort,” he said.

There were no injuries.

The fire burned about 25 percent of the flat membrane roof, Sanders said.

There was no water or smoke damage to the interior of the building, he said.

The fire was called in to the Peninsula Communications emergency dispatch center at 2:38 a.m. Tuesday.

The person said flames were shooting from the roof, Fire Department Capt. Kelly Ziegler said.

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Senior Staff Writer Paul Gottlieb can be reached at 360-452-2345, ext. 55650, or at pgottlieb@peninsuladailynews.com.