Fire officials on Monday were trying to determine the cause of an early morning fire that destroyed a popular Key Largo restaurant on Sunday. The building apparently was unoccupied at the time of the fire, and no injuries were reported.

Jennifer Hammer, owner of Snook's Bayside Restaurant, at Mile Marker 99.9, said she intends to rebuild, and hopes to reopen the outside tiki bar within the next few months.

Monroe County Fire Marshal Steve Zavalney said he did not yet know the source of the 4:20 a.m. blaze.

"Firefighters said by the time they arrived all the windows were blown out and the building was fully engulfed," he said. "We were not able to get in there this morning since the roof over the kitchen has collapsed."

The building was gutted by a fire so hot that some of its cinder blocks had melted. A waterside patio and bar had some damage, but a pier extending out on Buttonwood Sound was untouched.

Southbound traffic was halted as firefighters ran fire hoses across the highway. Traffic was impacted until about 7:15 a.m. as firefighting efforts continued, according to information released by the Monroe County Sheriff's Office.

State Fire Marshal Lt. Joseph Schwartz said the fire is under investigation, and his unit would methodically review natural sources to determine the cause. The state fire marshal is called to investigate when damage to a structure is extensive.

The Key Largo, Tavernier and Islamorada fire stations were called to the scene. In all, 30 firefighters battled the blaze.

Key Largo Fire Chief Sergio Garcia said he could see the flames from the traffic light on the Overseas Highway as he was approaching the scene.

"When I arrived I found the restaurant fully engulfed in flames," he said. "A power line had already come down, blocking the fire trucks from further accessing the property from the main driveway."

He said the incoming units had to use the south driveway between Cafe Largo and Largo Honda.

"Since we could not [contact] the owner and did not know if the building was occupied, Key Largo firefighters searched the first floor using the thermal imaging camera in the zero visibility conditions," he said, "and Islamorada's firefighters laddered the second story and searched for occupants."

Garcia commended all firefighters for working as a team.

sgibbs@keysnews.com