Without identifying them, the Oakland Fire Department said earlier that two pedestrians were hit by a passenger train at Jack London Square about 7:30 p.m. and taken to a hospital.
The accident was near Yoshi's, a jazz and R&B club where the group had been scheduled to play two shows Thursday night. Both were canceled.
It wasn't clear why the men were on the tracks, but pedestrians often need to cross them in the area with trains running across and in between streets, including right outside Yoshi's.
The Tower of Power, a band of about a dozen members, most of them horns, has been beloved members of the R&B and pop communities since forming in Oakland in 1968. The group and its rotating cast of musicians have recorded behind many far more famous names including Elton John, Otis Redding, Aerosmith and Santana.
They were also a national TV fixture in the 1980s with frequent appearances on Late Night With David Letterman.
Tributes and well wishes were quickly emerging on Twitter, including one from pop star and drummer Sheila E., who tweeted "Pleez pray for my frenz."
Tower of Power landed a total of nine songs on the Billboard Hot 100, with a No. 17 best for "So Very Hard to Go" for 1973.