#NEW: Diesel spill at the Alameda Marina near the Oakland Estuary, according to DFW. Amount unknown at this time. pic.twitter.com/PS1dRTEZBC — Chris Nguyen ABC7 (@ChrisNguyenTV) February 11, 2015

#MORE: Crews currently on scene for cleanup. Source of spill is unclear. Diesel smell remains in the air. #Alameda pic.twitter.com/QK2LWtkLN2 — Chris Nguyen ABC7 (@ChrisNguyenTV) February 11, 2015

OAKLAND, Calif. (KGO) -- A cleanup is underway in the Oakland Estuary, near Coast Guard Island, where there's been a fuel spill at the marina.It's unclear where the diesel came from and how much actually spilled into the area, but the sheen from the spill is about three-quarters of a mile long.The Department of Fish and Wildlife believe happened Tuesday night. The harbor master says he quickly alerted the National Response Center. Thee Alameda Fire Department initially responded.Crews from the coast guard, along with its contractors, have been out here since early Wednesday morning.They're using pads to soak up as much of the diesel as possible.Marina residents say the smell Tuesday night was absolutely unbearable."You always have a little bit of a smell, there are some old boats that tend to leak a little bit, but this was big. I looked outside and I could see, even though it was nighttime, it was blanketing the water," said Emmanuel Ievolella, an Alameda Marina resident.Many of the residents opted to sleep in their vehicles. Some ended up going to nearby motels as a precaution.Department of Fish and Wildlife and the coast guard did collect some water samples. They hope to have the results back in the next few days.