About 4 p.m. near Grant Avenue and Sutter Street, a witness says someone threw what looked like a quarter stick of dynamite through a restaurant's window.
Witnesses say three people took off running.
"I took off after them," witness Jonathan Danielson said. "They stopped at the corner right over there, so I got out my camera, my cellphone, and I took a picture of them. And as soon as I took a picture of them, they just took off running."
A window was shattered and a planter box damaged, but no injuries were reported.
Police have taken one person into custody, thanks to the witness' picture, and they continue to search for more.
Bomb sniffing dogs were brought in to see if there were any other explosives in the area, but have not reported any.