State officials don’t know why plastic and other debris littered the Ala Wai Canal all day yesterday.

Trash typically flows into the Ala Wai during heavy rain. But there was no deluge Wednesday night, and the lack of a current during Kona conditions meant the debris simply sat in the canal, said Brian Fuller, who exercises along the canal every morning.

Fuller is used to seeing debris in the Ala Wai — but nothing like what he saw yesterday.

"Most of it was plastic, and there was what looked like an oil sheen," Fuller said. "That was as bad as I’ve seen it over the years. I took notice because there was no wind, so it was just sitting there. Where did this come from?"

Various state agencies have jurisdiction over the Ala Wai Canal, said Debo­rah Ward, spokes­woman for the state Department of Land and Natural Resources.

State harbors officials are responsible for clearing debris once it collects in a trap on the Waikiki side of the Ala Moana Bridge, Ward said.

But she was unsure yesterday who is responsible for cleaning debris that simply sits in the canal.