Firefighters are battling a 4-alarm fire on Pier 45 in San Francisco

A quarter of the pier at Fisherman's Wharf "has been lost to the flames," according to the San Francisco Fire Department public information officer.

No injuries have been reported. The pier has been fully evacuated, the department says.

Flames could be seen in the early morning darkness in photos tweeted by Dan Whaley.

The blaze was first reported at 4:17 a.m. local time (7:17 a.m. ET) and has been contained to a section of the pier.

Officers report the fire caused a partial building collapse on the southern part of the pier, spread to two buildings on the pier and is in danger of spreading to a third, the Fire Department says. Pier 45 burns in San Francisco, with the Transamerica Pyramid in the foreground. Fireboat St. Francis was put in position to protect the historic SS Jeremiah O'Brien ship built during World War II, and it successfully saved the ship from damage, said Jonathan Baxter, the department's spokesman. "When firefighters arrived, the flames were literally lapping over the Jeremiah O'Brien," he said, CNN affiliate KPIX reported . "They literally saved the O'Brien." Reporter Reyna Harvey of affiliate KRON tweeted video from the scene. During this fire at pier45, the SS Jeremiah O'Brien a Liberty ship built during World War II and named after the American Revolutionary War ship captain Jeremiah O'Brien was saved from burning. pic.twitter.com/ykhY3rKCex — Reyna Harvey (@ReynaHarveyB) May 23, 2020 Several fireboats are positioned around the wharf and helping fight the fire. There is no word yet of a cause. The warehouse contained a large fish processing operation for the Northern California crab fleet, KPIX reports.