KANEOHE, Hawaii -- Honolulu police impounded a pickup truck they are calling a "vehicle of interest" in connection with the disappearance of a 21-year-old woman.

Masumi Watanabe was last seen on April 13 in Pupukea.

Police have searched parts of Oahu's North Shore and windward side looking for the woman from Japan.

A tip led officers with the Honolulu Police Department's Special Services Division and Department of Land and Natural Resources crews to the area surrounding Kawainui Marsh on Thursday.

Despite the day long search on foot, they still have not found any evidence of Watanabe's whereabouts. Items found on Wednesday in a search of Kahana Valley have not yet been determined to be connected to the case.

Police have impounded a white 2003 Ford F-150 pickup truck.

They interviewed the driver. Police are asking for any information from anyone who may have seen a Caucasian male driver or the truck in order to put together a time line of events and places.

"We are looking for anyone who saw the driver of the truck, or the truck in the area of Pupukea to Kaneohe, maybe the Honolulu areas the night of (April) 12th, and possibly throughout the week and the weekend on the 16th," said Sgt. Kim Buffet of HPD's CrimeStoppers.

An after market gas cap is a distinguishing feature on the four-door pickup truck.

"We know where it is. We know who it belongs to, but we're trying to see if the stories match up, and if we can place and put the vehicle at the scene, or not at the scene, or anything that anybody can give us out there," Buffet said.

Watanabe was last seen walking on Pupukea Road the morning of April 12.

Watanabe had been staying with a host family in Waimea since February and was scheduled to return to Japan on Thursday.