CLAYTON -- A fire that has left large parts of Mount Diablo charred and barren slowed in intensity Wednesday, allowing residents in unincorporated Clayton to return home and freeing up fire equipment and crews to battle other blazes raging statewide.

For the first time since the fire began Sunday afternoon, officials say the end is in sight: They are optimistic the fire will be fully contained by Friday.

"I've been watching the mountain all day long," said Cal Fire spokeswoman Tina Rose. "Not one puff of smoke has come off it."

As of Wednesday afternoon, the Morgan Fire was 80 percent contained and did not scorch as many acres as originally believed.

Fire crews walked the perimeter of the fire with GPS technology and said 3,133 acres have burned since the fire broke out about 2 p.m. Sunday on Morgan Territory Road near Marsh Creek Road. Originally, fire officials estimated 3,718 acres had burned.

The summit center atop the mountain, which holds the beacon lit every Dec. 7 to commemorate the 1941 attack on Pearl Harbor, has not been damaged, and Rose said that crews are guarding the structure "like a mama bear guards her cubs." The actual beacon light was removed from the structure in June for restoration

Rose said 1,372 firefighters have worked to contain the blaze since Sunday, and about 300 of them left Wednesday to fight other fires or go home to rest.

"If everything continues to go the way it has been going, we think containment will be fully complete by Friday," Rose said. "We're obviously very cautious in our predictions because you don't know what can happen. But we are optimistic."

The stabilization of the charred mountain also began on Wednesday. Rose said crews will spend weeks working to prevent mudslides from occurring when the rainy season begins.

An evacuation order for about 75 homes in the area was lifted Tuesday night. Several small remote outbuildings were destroyed, including sheds and a trailer at the Diablo Bowmen archery club, but no homes were damaged or lost.

Jacqueline Stewart, who lives on Curry Canyon Road, returned Monday, as did many of her neighbors.

"I just cannot say enough about the fire department here," Stewart said. "They protected this canyon way above and beyond. They are such heroes."

Crews are still investigating what may have caused the fire.

Contact Rick Hurd at 925-945-4789. Contact David DeBolt at 510-262-2728. Follow them at Twitter.com/3rdERH and Twitter.com/daviddebolt.