Updated Tuesday: The victim warned two other surfers about the attack, and they all paddled to shore after the attack

A shark attacked a Portland man who was surfing near Indian Beach on Monday, according to the Oregon State Police.

Early information indicates the shark bit Joseph Tanner, 29, on his upper thigh and lower leg, the Oregon State Police said in a news release. He was flown to Portland's Legacy Emanuel Medical Center for treatment of serious injuries, troopers said.

A medical center spokesman said Tanner was under evaluation in the emergency room, as of about 7 p.m. Authorities were dispatched to the beach, a popular surfing destination that's part of Ecola State Park, about three hours prior.

There hasn't been a shark attack off the Oregon coast since 2013, according to two online databases. The November 2013 attack happened off Gleneden Beach in Lincoln County.

Of 28 previous Oregon shark attacks listed in the Global Shark Attack File database, only one has been fatal. A California couple died in 1975 after a freak wave may have capsized a fishing boat they were operating 200 miles northwest of Astoria, .

The Oregon state medical examiner said Grace Conger died of several large shark bites and that her husband drowned.

An Oregon State University oceanography professor told The Oregonian it's plausible that blue sharks bit Oliver Conger's dead body, causing blood to enter the water and inciting a frenzy among other blue sharks.

Each of the 27 previous authenticated, unprovoked Oregon shark attacks have involved great white sharks, said Ralph S. Collier, director of the Global Shark Attack File and president of the Shark Research Committee.

There have been a few provoked shark attacks over the years, he said, but those cases are not included in the database.

An Oregon State Police spokesman said investigators don't know what kind of shark attacked Tanner.

Shark attacks off the West Coast most often happen from August through October, Collier said. Attacks are rare, he said, and more often than not happen in locations where there have been previous attacks.

"Even with these increases in both populations -- humans and sharks -- we still have very few of these when you look at the overall picture," he said.

Troopers are investigating Monday's attack.

-- Jim Ryan

jryan@oregonian.com

503-221-8005; @Jimryan015